What haven't I done?

Lots.

A meme zinging around the geoblogosphere asks "what have you seen?" (I've bolded all the I've done/seen.)
1. See an erupting volcano
2. See a glacier
3. See an active geyser such as those in Yellowstone, New Zealand or the type locality of Iceland
4. Visit the Cretaceous/Tertiary (KT) Boundary. Possible locations include Gubbio, Italy, Stevns Klint, Denmark, the Red Deer River Valley near Drumheller, Alberta.
5. Observe (from a safe distance) a river whose discharge is above bankful stage
6. Explore a limestone cave. Try Carlsbad Caverns in New Mexico, Lehman Caves in Great Basin National Park, or the caves of Kentucky or TAG (Tennessee, Alabama, and Georgia)
7. Tour an open pit mine, such as those in Butte, Montana, Bingham Canyon, Utah, Summitville, Colorado, Globe or Morenci, Arizona, or Chuquicamata, Chile.
8. Explore a subsurface mine.
9. See an ophiolite, such as the ophiolite complex in Oman or the Troodos complex on the Island Cyprus (if on a budget, try the Coast Ranges or Klamath Mountains of California).
10. An anorthosite complex, such as those in Labrador, the Adirondacks, and Niger (there's some anorthosite in southern California too).
11. A slot canyon. Many of these amazing canyons are less than 3 feet wide and over 100 feet deep. They reside on the Colorado Plateau. Among the best are Antelope Canyon, Brimstone Canyon, Spooky Gulch and the Round Valley Draw.
12. Varves, whether you see the type section in Sweden or examples elsewhere. [hand sample only]
13. An exfoliation dome, such as those in the Sierra Nevada.
14. A layered igneous intrusion, such as the Stillwater complex in Montana or the Skaergaard Complex in Eastern Greenland.
15. Coastlines along the leading and trailing edge of a tectonic plate.
16. A gingko tree, which is the lone survivor of an ancient group of softwoods that covered much of the Northern Hemisphere in the Mesozoic. [near my office, god the fruit stinks]
17. Living and fossilized stromatolites (Glacier National Park is a great place to see fossil stromatolites, while Shark Bay in Australia is the place to see living ones)
18. A field of glacial erratics
19. A caldera
20. A sand dune more than 200 feet high [Great Sand Dune National Park]
21. A fjord
22. A recently formed fault scarp
23. A megabreccia
24. An actively accreting river delta
25. A natural bridge
26. A large sinkhole [Lake Jackson, Florala, Alabama - largest sinkhole in the state]
27. A glacial outwash plain
28. A sea stack
29. A house-sized glacial erratic
30. An underground lake or river
31. The continental divide
32. Fluorescent and phosphorescent minerals [got a set one time as a present]
33. Petrified trees
34. Lava tubes
35. The Grand Canyon. All the way down. And back. [haven't been to the bottom]
36. Meteor Crater, Arizona, also known as the Barringer Crater, to see an impact crater on a scale that is comprehensible
37. The Great Barrier Reef, northeastern Australia, to see the largest coral reef in the world.
38. The Bay of Fundy, New Brunswick and Nova Scotia, Canada, to see the highest tides in the world (up to 16m)
39. The Waterpocket Fold, Utah, to see well exposed folds on a massive scale.
40. The Banded Iron Formation, Michigan, to better appreciate the air you breathe. [samples only]
41. The Snows of Kilimanjaro, Tanzania,
42. Lake Baikal, Siberia, to see the deepest lake in the world (1,620 m) with 20 percent of the Earth's fresh water.
43. Ayers Rock (known now by the Aboriginal name of Uluru), Australia. This inselberg of nearly vertical Precambrian strata is about 2.5 kilometers long and more than 350 meters high
44. Devil's Tower, northeastern Wyoming, to see a classic example of columnar jointing.
45. The Alps.
46. Telescope Peak, in Death Valley National Park. From this spectacular summit you can look down onto the floor of Death Valley - 11,330 feet below.
47. The Li River, China, to see the fantastic tower karst that appears in much Chinese art
48. The Dalmation Coast of Croatia, to see the original Karst.
49. The Gorge of Bhagirathi, one of the sacred headwaters of the Ganges, in the Indian Himalayas, where the river flows from an ice tunnel beneath the Gangatori Glacier into a deep gorge.
50. The Goosenecks of the San Juan River, Utah, an impressive series of entrenched meanders.
51. Shiprock, New Mexico, to see a large volcanic neck
52. Land's End, Cornwall, Great Britain, for fractured granites that have feldspar crystals bigger than your fist.
53. Tierra del Fuego, Chile and Argentina, to see the Straights of Magellan and the southernmost tip of South America.
54. Mount St. Helens, Washington, to see the results of recent explosive volcanism.
55. The Giant's Causeway and the Antrim Plateau, Northern Ireland, to see polygonally fractured basaltic flows.
56. The Great Rift Valley in Africa.
57. The Matterhorn, along the Swiss/Italian border, to see the classic "horn".
58. The Carolina Bays, along the Carolinian and Georgian coastal plain
59. The Mima Mounds near Olympia, Washington
60. Siccar Point, Berwickshire, Scotland, where James Hutton (the "father" of modern geology) observed the classic unconformity
61. The moving rocks of Racetrack Playa in Death Valley
62. Yosemite Valley
63. Landscape Arch (or Delicate Arch) in Utah [maybe, but I'm not sure]
64. The Burgess Shale in British Columbia [samples only]
65. The Channeled Scablands of central Washington
66. Bryce Canyon
67. Grand Prismatic Spring at Yellowstone
68. Monument Valley [again, I don't remember everywhere we went that summer]
69. The San Andreas fault
70. The dinosaur footprints in La Rioja, Spain
71. The volcanic landscapes of the Canary Islands
72. The Pyrennees Mountains
73. The Lime Caves at Karamea on the West Coast of New Zealand
74. Denali (an orogeny in progress)
75. A catastrophic mass wasting event
76. The giant crossbeds visible at Zion National Park
77. The black sand beaches in Hawaii (or the green sand-olivine beaches)
78. Barton Springs in Texas
79. Hells Canyon in Idaho
80. The Black Canyon of the Gunnison in Colorado
81. The Tunguska Impact site in Siberia
82. Feel an earthquake with a magnitude greater than 5.0.[only a 3.5]
83. Find dinosaur footprints in situ
84. Find a trilobite (or a dinosaur bone or any other fossil)
85. Find gold, however small the flake
86. Find a meteorite fragment
87. Experience a volcanic ashfall
88. Experience a sandstorm
89. See a tsunami
90. Witness a total solar eclipse
91. Witness a tornado firsthand. [thank God, no]
92. Witness a meteor storm, a term used to describe a particularly intense (1000+ per minute) meteor shower
93. View Saturn and its moons through a respectable telescope.
94. See the Aurora borealis, otherwise known as the northern lights.
95. View a great naked-eye comet, an opportunity which occurs only a few times per century
96. See a lunar eclipse
97. View a distant galaxy through a large telescope
98. Experience a hurricane
99. See noctilucent clouds
100. See the green flash

Apparently there were some complaints that it is US-centric so Callan Bently wrote up a slightly different one:
Specific places

1. Visit the Chalk (England, France, Ireland...) [I've seen the Selma chalk]
   
2. Visit Iceland
3. Visit Mt. Fuji, Japan
4. Visit Great Barrier Reef, Australia
5. Visit the Himalayas (Kashmir?)
6. the Tibetan Plateau
7. Visit the Gobi Desert
8. Visit the Sahara Desert
9. Visit the Sonoran Desert (for the saguaros)
10. Visit the Atacama Desert
11. Visit the Rub' al Khali (Empty Quarter)
12. Visit Beijing or Shanghai (for the perspective on what really dirty air looks like)
13. Visit the big island of Hawai'i
14. Visit Yellowstone
15. Visit the Galapagos Islands
16. Visit Madagascar (for the lemurs)
17. Visit Patagonia
18. Visit the Andes
19. Visit the Alps
20. Visit the Canadian Rockies
21. Visit Wrangell-St. Elias National Park, Alaska (and/or neighboring Kluane National Park in the Yukon Territory)
22. Visit Denali, Alaska
23. Visit the Aleutian Islands
24. Visit Chimborazo, Ecuador (furthest point from the center of the Earth, due to the equatorial bulge)
25. Visit Antarctica
26. Visit the Siberian Traps
27. Visit the Deccan Traps
28. Visit the Columbia River flood basalt province
29. Visit Sumatra/Krakatau/Java, Indonesia
30. Visit the South Island of New Zealand
31. Visit the Appalachians
32. Visit the Dead Sea
33. Visit the Giant's Causeway, County Antrim, Northern Ireland.
34. Visit the Great Rift Valley of East Africa
35. Visit the Nile River
36. Visit the Mississippi River
37. Visit the Amazon River
38. Visit the Grand Canyon
39. Visit the Owens Valley, California (or anywhere in the Basin & Range, but the Owens Valley is pretty darned special, and geologically diverse)
    
40. Visit Gros Morne National Park, Newfoundland, Canada (walk on the "Moho")
41. Visit Siccar Point, Scotland (for the unconformity)
42. Visit Gibraltar, "UK"
43. Visit Vesuvius, Pompei, and the Pompei-to-be, Naples
44. Visit Uluru (Ayers Rock), Australia
45. Visit the Moon

Geological features

1. A tectonic triple junction (Mendocino, CA is an example, or northern Burma, or Panama)
2. Tower karst (Guilin, China, or southwestern Thailand are examples)
   
3. A regional flood
4. A flash flood
5. Ediacaran fauna fossils in situ (possibilities include the type locality of the Ediacaran Hills in Australia, or Charnwood Forest in England, the White Sea region in Russia, or maybe the Avalon Peninsula in Newfoundland)
6. Vertebrate fossils in situ
7. Visiting a laggerstatten site (Burgess Shale, Chenjiang, Sirius Passet, Solnhofen?)
8. An alpine glacier
9. A continental glacier (ice cap or ice sheet)
10. A kimberlite pipe (preferably with diamonds, and good luck with that) [in Arkansas]
    
11. A coral atoll (take your pick)
12. A meteor impact crater (not a buried one, either)
13. A big river delta (Mississippi, Ganges, Nile, or any of the dozens of others)
14. Barrier islands (Padre Island, Texas, and the Outer Banks of North Carolina come to mind, but I'm sure there are others on other continents)
15. A craton (Canadian shield, Kaapvaal, North China, etc. etc. etc.)
16. A big estuary (Cook Inlet, Chesapeake Bay, Bay of Fundy: all North American examples. Give me some others)
17. See some karst.
18. Kayak (or other boat) through a fjord.
19. See a dropstone.
20. See an ophiolite.
21. Visit a major stike-slip fault (San Andreas in USA/Mexico, or North Anatolian in Turkey, or Tan Lo (sp?) in China)
22. Visit a nappe or thrust sheet (Glarus Thrust in the Alps, Chief Mountain/Glacier NP in Montana, Blue Ridge in Virginia/North Carolina)
23. Visit a really big cave (Mammoth, Lechugilla, or some other that I don't know about on another continent)

Activities and experiences

1. A world-class natural history museum (London Museum of Natural History, American Museum of Natural History, and the Smithsonian's National Museum of Natural History all come to mind.)
2. Meeting of a classic scientific society (Royal Society, Explorers Club, Cosmos Club...)
3. Do some original research.
4. Present your research at a meeting of other scientists.
5. Publish your research in a peer-reviewed scientific journal.
6. Visit an original copy of "map that changed the world" (William Smith's geologic map of England, Wales, and part of Scotland)
7. Experience a big earthquake (greater than 5.0 sounds like as good a cut-off as any)
8. Experience a volcano erupting something other than gases (lava, pyroclastics)
9. Go ice fishing (or just out onto a frozen lake/pond/sea/ocean and ponder the improbable nature of ice and how it freezes from the top down, preserving the living things underneath, like fish. Without this odd property, it would be tough to maintain life in our high-latitude/elevation lakes/etc. through the winter months.)
10. Compare and contrast El Nino and La Nina.
11. Go on an oceanographic research cruise for more than two weeks at sea.
12. Experience a hurricane/typhoon/cyclone (preferably with surviving it as a caveat)

Oringinal list 24/100, Bently list 16/100 for those counting. I obviously have a way to go.