I geek out on a lot of stuff, for anywhere from ten minutes to a week... then I get bored or distracted and move on to something else.
Books (science fiction, fantasy, classical literature (I have a BA in English), philosophy, physics (Hawking <3), psychology, mythology (Campbell <3), tech, and my next love affair is going to be with History I think)
Photography (but I can't afford a good camera)
Music (gigs of mp3s, rock, jazz, classical, "new age")
RPGs (online (Everquest, etc), offline (D&D, etc))
Game design (I have ideas for a dozen Facebook games, but the Facebook API and performance suck)
Graphic design (I have hundreds of megs of books just on graphic design and advertising psychology)
Web design
Comics
Programming
Games (playing)
...
The list goes on. Sometimes it feels like my brain is on fire.