Chess Puzzles by Grandmasters: Contains problems found in games played by Grandmasters. Sorted by Grandmaster, opening, or year

Chess Tactics Server: Interactive site, contains over 20,000 chess problems, puzzles and members rated by Glicko rating system

Chess Videos: Learn by watching expert chess videos or upload your own video for discussion in the forums

Farnsworth's Predator at the Chessboard: A free comprehensive online book detailing hundreds of chess tactics using diagrams and examples