Sweet.
According to tech site Ars Technica, the Windows 7 Release Candidate will be available to the public starting in May 2009, will be available through June 2009, and will expire June 1, 2010. We'll keep our eyes open for a specific date in May, and keep our fingers crossed that Microsoft doesn't underestimate the web like they did with the beta release. Check out Ars for more details.
Windows 7: Windows 7 Release Candidate Coming to Public May 2009