I'm a peculiar sort of wanderlust. I have only a marginal interest in going to see places that make it to "seven wonders" status, like the Pyramids or the Coliseum. When I look at a map -- or Google Earth -- my eyes are drawn to the most touristically-neglected parts of the map, as well as countries with unpronounceable names, barely-navigable terrain, and desolate, wide-open spaces. Last night a friend was telling me about his trip to Uzbekistan and Tajikistan, and I found myself becoming unaccountably jealous. I've never been to any 'stans!
We're planning a trip to Eastern Europe next year -- Poland, Hungary and the Czech Republic -- and that should help ease the pangs of wanderlust a bit, though I'll probably end up wishing I'd gone 10 or 15 years ago. Last spring I made it to Death Valley, and that was breathtakingly remote and beautiful (and surprisingly filled with cool and varied things to see).
The Sierra Club just released a custom Google Earth map marking "the 52 wildest places" in North America (with an eye toward keeping them that way). I've been to a few of them: the Everglades (I grew up in Florida) and Oregon's Mount Hood.
A few places on my global to-do list: Greenland, Alaska, Siberia, Northern Canada, Tierra del Fuego, Madagascar. What's the wildest place you've ever been?