One thing I really love to do (although not more than eating) is reading. I can easily go through 10 or 15 books in a month, and I started saving oodles of money when I made the switch from bookstores to my local library (or three local libraries, to be more precise). I read a lot of nonfiction, and one subject that I read a lot about is food. I'm interested in the industrial food complex, and how to avoid it as much as possible. This includes being vegan, eating as much organic produce as I can afford, avoiding food products (read Michael Pollan's In Defense of Food for more information on food products), and trying to grow as much food as I can indoors.
It's amazing how simple it can be to grow some things indoors. I have north facing windows, a tiny apartment, and until recently had quite the black thumb, but I have still managed to produce quite the little indoor garden. However I didn't know until last summer that it was possible to grow a few veggies with little to no effort involved.
The first thing I learned how to grow was scallions. This is real simple: take the bottom part (with the root attached) and either plant it in a small pot, or stick it in a jar of water. They'll grow really big, and you can just cut the top off when you're ready and eat it. It'll grow back. I'm not sure if there's a limit to how often it'll grow back, but it's certainly better than going to the store to buy more!
The second thing I learned was in an awesome resource, Urban Homestead. It was a short paragraph on growing garlic. Similarly to the scallions, you simply plant the garlic clove in some dirt and prune and eat the shoots. I had my first garlic shoots yesterday and they were simply delicious. They are very garlicky, without going through the effort of peeling and chopping up a whole clove.
I've also planted an onion (it was sprouting an awful lot in my fridge), but I have no idea yet if the shoots are edible. But it looks cool and hasn't died (yet), so I'll keep it going for as long as I can. Also indoors I have some peppers sprouting (thai, ho chi minh and habañero) as well as some seeds just planted (red, green and jalapeños). On my fire escape is a bucket full of lettuce plants that are somewhere between a sprout and baby lettuce. They're still delicious (just slightly spicy) in a salad.
I've probably sunk about 20$ into the whole deal, mostly the lettuce seeds (which were 7.50$ at Whole Foods) and also including potting soil. But if the pepper plants grow to produce actual peppers, I'm sure this is money I'll easily be saving by not going grocery shopping as often. Also, it's cool to grow your own food!