Chess program that plays many variants
Sjeng is a chess program that plays normal chess and many variants like crazyhouse, bughouse, suicide (aka giveaway or anti-chess) and losers. It can also play variants which have the same rules as normal chess, but a different starting position. It uses the XBoard/WinBoard interface by Tim Mann, so it can be used with xboard or eboard. It is also capable of playing on internet chess servers.