Activities: My favorite is definitely dancing (Metal, Trance, Pulse, Reggae, and HipHop), I enjoy Bicycling when the weather is nice, DND game sessions, and I've come to fancy Karoke (especially Korean style Noreban, which is the same idea except that you and your friends have a private room and you feel more confident)
Collections: Comic books, Coins, and Action Figures. In the summer, when I happen to be living near a beach, I walk the shoreline looking for beach glass (It's a really therapeutic way to clear your mind of stress)
Diversions: Movies, Music, Driving in the countryside, Bars and Pubs (especially when they have a pooltable)