HEre are my two cents; join a choir (I have!), take drawing or painting lessons, volunteer (don't just go to but participate in the organization of) at a sci-fi or other kind of mutual interest / fandom society (I'm in one that organizes SF conventions, among them, the biggest in Norway).

For my new challenges, at some point I will take solo singing lessons, go to karaoke bars and actually blow everyone away with great singing (Though I heard somewhere that the word karaoke means "I'm drunk and I can't sing", some karaoke ppl really can. Won't argue with the drunk bit, though!), I will go on a week-long SPA holiday in Estonia (That's actually pretty cheap, which is why Estonia.), and I plan to start training Kung Fu.