I posted the 2D platform game engine that I am working on in the "In progress" forum (source included). It's a Mario clone (all graphics are copyrighted by Nintendo of course). I know, no one wants to play a Super Mario hack but I am just doing it to create the game engine. Actually, I would also like to make a simultanious multiplayer SMB1 game! How cool would that be! You could battle for coins and powerups, jump on each other's head. I think that would have seriously cool game play potential. I just know I'll never have time to work out the networking code. I'm still far from even thinking about doing that yet anyhoo.
http://forum.thegamecreators.com/?m=forum_view&t=37129&b=8

He's evil, but, he'll die. I like it.