A couple of my "hobbies" revolve around saving money, like reloading.
I couldn't afford to eat out more than a couple times a week, so I learned to cook. Since I'm a geek, I needed to learn about food chemistry and experiment with all kinds of cooking-related stuff. My mom is now jealous because my knife skills are better than hers. Side benefit: women love guys who can cook.
I also got into old-school shaving to save on razor blades. Thankfully, I didn't get sucked into it as much as some people (I have no plans to buy a $400 Rooney brush anytime soon). I have enough blades to last me 2 years and it cost me $20.
Apart from that, I spend a lot of time doing computer-security-related toy projects. I've spent a lot of time on wargames like smashthestack.org and I've started reverse-engineering various crackmes. I've done a little malware reversing and I'm trying to get better at that.
Building electronics. Right now I'm building an alarm system for my house, I just need to get a laser printer so i can etch some boards. On that note, anyone got an old laserjet they want to get rid of?