Solitaire Central 
Rules, descriptions, and pictures of patience games. Also offers web-based game software.
http://www.solitairecentral.com/BVS Solitaire Collection
Provides introduction and rules for a several original solitaire variations.
http://www.bvssolitaire.com/rules.htm
Card Games: Competitive Patience
Rules for four variations of multi-player patience (solitaire) and links for one-player games.
http://www.pagat.com/patience/
Solitaire Strategy by ChessandPoker.com
Nine-step decision making process that guides a player to the correct play. Also presents specific strategies for Klondike.
http://www.chessandpoker.com/solitaire_strategy.html
Solitaire Laboratory
Features solutions and descriptions for Freecell, Giza, Pyramid Puzzlements, and Fourteen Out.
http://www.solitairelaboratory.com/
United States Playing Card Company: Solitaire Games
Features rules and instructions for multiple variations.
http://www.usplayingcard.com/gamerules/solitairegames.html
dogMelon
Provides rules, descriptions, and graphical examples of multiple solitaire games.
http://www.dogmelon.com.au/solhelp/
Semicolon Software
Features articles about winning at multiple solitaire variations.
http://www.semicolon.com/Winning.html
