Bitcoin Foundation: Created with the mission to standardize, protect and promote Bitcoin. Offers information about the foundation, the board, its governance; and how to become a member

Bitcoin Project: Official site offering documentation, forums and the open source client software which permits to send and receive bitcoins

Bitcoin Talk: The main Bitcoin discussion forum, includes subforums for technical support, mining, development and economics

Bitcoin Wiki: Contains a number of articles about BitCoin wallets, mining, trading, myths and other useful information