I have always wanted to go to the Galapagos islands, that is a big "must" on the travel destinations list; that and Cuba (for the jazz, cigars and general awesomeness), Malaysia (for the jungle, diving in islands close to it, and again general awesomeness), and Russia/Eastern Europe.
My best holiday yet was three months well spent in South America, seeing some amazing sights. Spent lots of it in Argentina, great wine, food, scenery - Ushaia and the national parks in particular are incredible.
+1million for skiing - I love the three valleys for the scenery, atmosphere and great slopes, but it does get a bit too rammed and touristy for my taste sometimes. I like to feel alone on the mountain, and often pray for slightly crappy weather to make sure that I am. California was a great experience, as was Quebec, Argentina had some wicked powder, but my favourite so far has to be Mayerhofen. What do you ski on Mike?