I've got too many hobbies to name... but the "big" ones cycle back and forth.
I have been really into video games but with the kid, there's very little time. I do have three arcade games in the basement - a Baby Pac-Man (combo pinball/arcade game) and two that are about 85% done to become MAME machines (one with a vertical monitor, one with a horizontal.)
Last year, I got into paper modeling a bit - you print patterns on heavy paper with your printer, cut them out, and glue them together. You can build some extremely complex things. There's a site out there that has scans from a German Disney magazine from many years ago that used to have these; I've built one (a space-themed mobile) for my kid's room, and have a rather large paper Cinderella Castle nearly done. I've also tried to do some car ones - those can get
really complex! There are ones for the Tower of Terror and other Disney landmarks, too - some are 15-20 pages of paper to work on!
Like Mark, I'm big into movies... the ability to do a theater was a huge factor when buying our house. We got a nice deep dry basement and my father and I built the theater ourselves. It's not quite 100% done (still need "proper" seats, fabric on the walls, a few other finishing touches) but is completely functional. It's wired for 7.1 but has 5.1 speakers now, a high-def projector (720p, I want to upgrade to 1080p now that it's affordable but having a hard time justifying the cost yet), and a screen that's somewhere around 103". Stadium seating, soffit lighting, X10 control, storage for around 1,300 DVDs, even an 8mm and 16mm projector and lots of 35mm film reels from the Eastman House, too.

I don't have any good current photos of it, though.
There are other hobbies too, but my big one (in terms of passion and cost!) is cars! I
love rallying (specifically WRC), which is basically street-legal (but exotic, like $500k-750k cost) cars going flat-out one at a time on real roads, including different surfaces (gravel, tarmac, snow, ice, mud, whatever). The cars spend a lot of time in the air and sideways, and it's extremely exciting. Naturally, that means that I have to have a street-going rally car for my daily driver... (forgive the slightly blurry shot from my old Minolta PnS)
That's my son, about 15 months old at the time, in his Subaru World Rally Team outfit, on my 2005 Subaru WRX STi. AWD, 6-speed, 300hp... it's a total riot.

I had a 2002 WRX beforehand, and we worked a couple SCCA ProRallys in Pennsylvania in the car before my kid came along.
Now, if I want something more classic, I've also got a 1966 Lotus Elan S2, which is a rather legendary car in sports car circles and was the direct inspiration for the original Mazda Miata (which is bigger, slower, and worse-handling!) I take it autocrossing occasionally but it barely gets driven in the past couple years, since I usually have to pick up my son every day after work and I'd probably be arrested if I tried to strap a car seat into this car! I have also been able to drive it on the Watkins Glen racetrack a few times but not at full speed.
I like my garage a lot - I wouldn't trade either car for anything else on the road.
But overall, right now, my two biggest hobbies are photography... and playing with my son, who really is the biggest joy in my life. (This is really saying something as I was a totally confirmed baby-hater before he came along!) Here he is after playing in the snow a few months ago...