I do not have much spare time, but when I do, I either grab my camera and go take pictures of stuff, grab my megatar and annoy the neighbors with my complete lack of musical prowess, or work on my website. On the weekends I go rollerblading or extended photo shoots (this weekend I'm thinking of going to the zoo to try out my new zoom lens
)
You need to pick up a hobby - something you enjoy doing "just because".
I will recommend the thing I am most familiar with: photography. Got a digicam? Great! Don't have one? Buy a Canon film SLR that accepts EF lenses. They are relatively cheap, and will get you off to a good start incase you get GAS (Gear Acquisition Syndrome
) and feel like buying a DSLR. Its a very rewarding experience.