I build robots, 3d printers, and other mechanical things. I design, build and debug electronics. I'm also trying my hand at furniture (built http://imgur.com/a/HLbWF yesterday). I also cook a lot.
I play violin. I consider playing it to be valuable to my own piece of mind and play for others on occasion. I'm sure I'm not the only amateur musician on HN though.
I help people who are new to computers or non-computer-savvy build their own PC's from components to save them getting shafted by companies that sell PC's wholly.
I fix and tune cars - I'm in my Honours year of a motorsport engineering degree. Right now I'm working on dramatically reducing the weight of my Citroen C5.