Computing.Net Windows XP Forum: General technical support discussion board. Free membership.
PCbanter: Topics include the basics, performance and maintenance, hardware and XP, customizing Windows, Messenger and networking.
Software to Hardware: Collected Articles from Windows XP Forum.
Tech Support Guy for Windows XP: Free technical support forum run by volunteers offering help to users of Windows XP.
The Green Button: A Community for enthusiasts of Windows Media Center Edition.
Windows XP Central: Includes news, forums, drivers, and downloads.
Windows XP certification forum: Dedicated to the Windows XP operating system and Windows XP certification exams.
Windows XP Support Forums: A general discussion and support forum.
WindowsXP-L Technical Discussion: A mailing list for the technical and functional discussion of Microsoft Windows XP.
windowsXPgroup: A discussion group. Free membership required.
ZDNet's Windows XP Forum: A general support discussion board. Includes downloads. Free membership.