I've dabbled in quite a few games over the years (MTG, Star Wars, pokemon). I still play a bit of Lord of the Rings TCG with friends. But the big one for me is Decipher's Star Trek CCG, which is still alive and well! (head over to www.trekcc.org
if you're interested!) Love that game and have stacks and boxes all over my home office.
There is a great program out there called Lackey CCG that has LOTS of plugins for various games. Paired with Skype it is really cool for playing games when you don't have folks near you. I used it just the other night to play LotR TCG with a high school buddy.