Despite GameSpy's shutdown, several multiplayer games that relied on its technology are still playable online, according to a list complied by ModDB users Rorisup and TKAzA.
GameSpy Technology announced its closure in early April, and operations that included leaderboards, friends lists and multiplayer matchmaking ceased May 31. In the wake of that announcement, several independent projects have created workarounds to keep games alive online. You can see a listing for 12 surviving games, including Crysis, Battlefield 1942 and Medal of Honor: Allied Assault, at ModDB.
Since the announcement, developers have also unveiled official solutions, including Bungie for Halo: Combat Evolved and Capcom for several games. In April, Electronic Arts said that it's looking to keep three older Battlefield titles online.