So our friend Troy turned 42 this weekend, and to celebrate held the first (hopefully) annual Troy Con, which was essentially an all-day orgy of board and card games interspersed with pizza and wings. He even went so far as to make up convention programs and souvenir buttons, and at one point we had three tables with three different games going on with about four or five players each. The only rule was that video games were forbidden (he's not much of a console guy), but we wouldn't have had time. We played everything from Carcassone to Catan to Puerto Rico. We played a spirited game of the Paranoia card game, did some liar's dice for a while, and a bunch of others -- he literally had at least $2000 worth of board games to choose from.
Probably my favorite was called Tsuro, which involved placing tiles with various patters of lines on them on a board, and your piece then had to follow the line adjacent to it, no matter how many tiles the line moved through (they all connect somehow). The object is to not run yourself off the board, which of course gets progressively harder as more tiles get placed. It's really simple to learn, a lot of fun, and there's no counters or even words on the board, so kids can play it and there's no language barrier.
All told, we started around 10:00am and there was a game of Betrayal at House on Haunted Hill still going when I left at 9:00pm, so I'd say it was a rousing success.