I dunno if I really have a "main hobby" any more ....
I used to be a real hardware/gaming junkie, but I haven't upgraded my gaming PC in two years, and it looks like I won't be upgrading any time soon.
I went through several years of being a Linux/BSD junkie, but now I'm down to just 2 Linux boxes, one of them my server, and the other one my HTPC. I broke down and bought a wireless router last year after my OpenBSD router died. (it was an old compaq celeron box with 128mb of ram)
I am a bit of a home theater/movie junkie still, I probably watch 3 or 4 movies per week, but that's not as much as I used to watch.
I bought a handgun last year and go to the range every now and again, it's fun and it's a great stress relief.
I like making fires, and now that it's not freezing outside in the evening, I make bonfires in my fire pit a few days per week, it's very relaxing and I also enjoy eating marshmallows