Microsoft's Kinect launches tomorrow and sadly there's very few co-op titles to play.  But if you are looking to flail around your living room to a classic Sega franchise with a friend on a virtual hoverboard - look no further than Sonic Free Riders.    As Tally previewed in our coverage of the game, there's two modes of co-op play.  In one mode called Tag Racing players can join hands and fuse their boards to get extra speed while racing.  In another mode called Relay, players race in a typical relay like fashion to win the race.