http://www.2dfighter.com
it's a p2p emulator network, you can play all those awesome 2d arcade fighters online like pretty much every single Street Fighter and King of Fighters. You need to download the roms (you can easily google them) and then they play through the emu program. Fun stuff, very little lag cause you can see what the connection is like to someone before you challenge them AND it's ranked on some games. Gamepad supported of course also.