My favourite social game ever? Hand and Foot, the card game. I've seen many variations of the game, but the rules I play by are
here.
Case has a few video games she likes, and so we play Baldur's Gate on PS2, Mario Party and SSX Tricky on the Gamecube, and maybe, just maybe, I'll get her to play Halo with me (Thanks, Dave!). At one point she liked playing Soul Calibur on the DC, but for some reason SCII isn't high on her "must play" list.