Hi Billy Optimist,
if you speak German, check out the German version of my fraternities home page. The English version is fine, but the German version is much more extensive.
http://www.kdstv-bodensee.de
And for the topic: boy that is a hard question!!!
nature wise, I'd go for Yosemite in winter, the Mojave desert and the Kyclad (?) islands in Greece (haven't been to tropical islands, yet, though)
best cities: North America: NYC, San Francisco, Toronto
Europe: there are so many - I love Rome but there are a lot of 2nd places!