Brandon LeBlanc has made the official public announcement that the RC Build of Windows 7 will be available for download on the MSDN and TechNet subscription sites on April 30, 2009, and to the general public on May 5, 2009. Of course if you like to live a little more dangerously, it is already available on your favorite BitTorrent site.
CC Hameed has information about how you can install Windows 7 from a USB thumb drive and how you may be able to install the release candidate build on top of the Beta 1 build. I always think it is better to do a fresh install for things like operating systems and SQL Server.
News also broke on Friday that higher end SKUs of Windows 7 will have a fully licensed copy of Windows XP Professional SP3 that will run virtualized, called Windows XP Mode (XPM). Joe Wilcox has more information about XPM here. It will be a separate download from Windows 7 itself.