I try not to collect things as a hobby as that just creates a clutter and maintenance problem. I try to make my hobbies about doing things instead of having things. The only thing I collect is albums.
One of my more interesting but very geeky hobbies is creating websites, blogs and forums around my interests. Of course it helps that I am a web designer and internet marketing consultant as a profession. I find building an audience or creating an online community completely fascinating. Although sometimes it's like babysitting. LOL I also do some "affiliate marketing". It's great to have a hobby that actually makes money. Last year I pulled in almost $40k net with this "hobby".
I also like gourmet cooking, skiing, kayaking, backpacking, fishing, craft beer, guitar, traveling and live music. I used to be a fish tank geek but it's dry and in storage right now. None of those are goofy I know. That's a good thing I guess. LOL.