I have loads of 'em... not many that I actively participate in because of lack of money. I consider guitar as a hobby, because I rarely play out and don't have the right discipline to practice.
HO scale model trains.... I absolutely love building realistic models and making realistic scenery to fit it. It's kinda like playing God except that you cannot make the people come to life. One thing I found out from all this modelling is that I got hooked on doing the research, history and figuring out how to execute all the numerous details that make the models look right. The biggest bug to me is what I call phoneyness.... or the lack of plausibility. Compact is often too compact to look the way it should. A perfect example of this is having a small rail siding built going into an even smaller building lot.... the railcar parked on the siding is pretty much bigger than the structure itself.
Astronomy... love this stuff too. Realizing that we can see back into time with our own eyes is mind blowing to say the least. I joined the ATMOB some years ago and learned that I had yet another expensive hobby. I have a 10" telescope mirror I made myself that I have been told is worth about 1200- 1800 bucks IF I could buy it commercially. Alas, I cannot afford to finish the telescope housing that mirror the way I want to.
Cooking.... for me, this a huge part of who I am. I am constantly experimenting with food and different cuisines. Take Japanese for example.... I got totally sick of dropping big money on restaurant sushi. So I learned to make decent stuff on my own. Problem is, I found I only save money if I outlay big bucks buying top quality imported ingredients and stretching those out. I save money buying fresh local seafood and other items. I am not scared to cut up a flounder nor a big lobster destined to become soup, sashimi or a maki roll.
Computer games on the PC... loads of fun when they run the way they are supposed to.