Microsoft Virtual PC 2004 is now free. PowerPC Mac users can now run Windows in a window for just the cost of a Windows license.

Virtual PC 2007, with support for Windows Vista, will be a free download starting next year. But will it run on Intel Macs? (VPC 2004 does not.)

Update: Damn fine print. Virtual PC for Mac is not free, only some other edition of Virtual PC which I guess is for running virtualized instances of older (or equal) versions of Windows on a Windows machine.