Windows 7 Release Candidate looks like it has been released a few hours early. I actually made it to the download page already and am currently downloading the 32bit version, if you get an Access Denied page, or the Java client fails, turn off java and try again. Microsoft also informed me that you will not be limited the the number of times you can download the RC and get keys to activate it. Check out some other important info MS included in the email.
Quote – Windows 7 Release Candidate Announcement
Thank you very much for your help in testing the Windows 7 Beta. Your feedback is invaluable in helping make Windows 7 a high quality operating system. With your help, we have reached the next major milestone on the journey to Windows 7: the Release Candidate (RC).
Microsoft suggests that you do a clean install instead of upgrading to help them fix bugs present in the Release Candidate. Here is the Windows 7 RC Install Instructions page with all sorts of helpful links to get you started.