These are useful sites to know:

Official Wizards of the Coast Websites

• The Official Dungeons and Dragons Website
• The D20 System Homepage

Other System Reference Document Websites

• The Hypertext D20 SRD
• http://systemreferencedocuments.org/
• SwoRD - The System wide-open Reference Document

Fansites

• Dungeons and Dragons Adventures
• Aarg!.net
• Weekend Warriors RPG group website