I'd say my main hobby is vintage cars. Well, I say vintage cars, but I really mean Citroëns. And only those with hydropneumatic suspension. No other suspension is good enough for me. As such, I have a 1974 Citroën DS 23 and a 1998 Citroën Xantia Activa V6.
It's fine to describe it as my main hobby, since I spend most of my money on that. But second in line is my computer(s) followed by board games, including designing them. Although, I've had little success in the latter part. Well, I also tend to lose when I play board games, so I dunno about success in playing them either.
I am a software developer by trade, but I also do like developing small programs at home. Either for fun or for some additional payment outside my regular job.
Then I also have a thing for studying/debating history/politics. I might consider myself a history buff, but really there is still so much to learn.
Recently I've found fountain pens, and hopefully soon, I'll get properly into typewriters. But that's very new to me (I don't even have a typewriter yet!).