BoardGames.About.com has rules for classic, unbranded board games and for several brand-name board games as well. Game manufacturers such as Hasbro, Mattel, University Games and Wizards of the Coast provide game instructions on their websites.
BoardGames.About.com provides both game rules and play strategies for classic games such as checkers, backgammon and mancala, in addition to brand-name games such as Scrabble and Monopoly.
Hasbro.com's game rule book search feature allows searching by game name or product number, and it includes games such as Clue, Candy Land and Life. Some of Mattel's game instruction PDF files are available or the Harry Potter Diagon Alley Board Game, Barbie of Swan Lake Board Game, and The Magic 8 Ball Board Game. University Games has rule books for The 39 Clues: Search for the Keys, the Dr. Seuss Trivia Game, and the board game version of Myst.
Wizards of the Coast is a subsidiary of Hasbro. Inc., but some of its rules for games such as Axis & Allies, Diplomacy and Avalon Hill's Battle Cry, are on the Wizards.com website. Others, such as some versions of Risk, are available on Hasbro's website.