Connectix Knowledge Database — This database, maintained by Connectix, contains hundreds of useful VPC-related tips and tricks.
Connectix User Forums — These are the official user forums for Virtual PC. Connectix support staff and engineers often make appearances on these forums, so it’s a great way to get your questions answered.
MacFixIt — This site contains tips for nearly every piece of software and hardware related to the Mac. Their interactive forums are a great place to post questions and receive answers about software and hardware problems.
Macintouch — Another great site for following Mac news and finding solutions to Mac-related problems.
MacWindows — A site dedicated to discussing issues involving Mac / Windows integration.
Emulation.net — A great site for Mac-based emulators of every type. It contains a great review of Virtual PC including screen shots and comparisons to other Mac-based PC emulators.
XLR8YourMac — Discusses ways to improve the speed of Virtual PC and upgrade your Mac hardware.
TidBits — Contains up-to-date Mac news, with a great searchable archive of past stories.