Download chess playing software and play chess with a computer!

Free Chess Playing Software Programs

listed at en.wikipedia.org/wiki/Chess_engine

Commercial Chess Playing Software Programs

Chessbase: Fritz, Junior, Shredder, Zap!Chess, Chess Tiger, Chesster: www.chessbase.com/shop/
Chessmaster by Ubisoft: www.chessmaster.com
Lokasoft: Chess Partner, Ktulu, SmarThink, Gandalf, Ruffian, Deep Sjeng, Rebel: www.lokasoft.nl/products

Rybka: rybkachess.com

Chess Genius: www.chessgenius.com
Hiarcs: www.hiarcs.com

Supercomputer Chess Engines

Hydra: www.hydrachess.com/main.cfm
Deep Blue: www.research.ibm.com/deepblue