So the Windows 7 Release Candidate (build 7100) was just released for the general public to download and test run today. I'm currently running the Windows 7 Beta (build 7000) and so I just had to give the new one a try.
[Download Windows 7 RC1 straight from Microsoft]
Build 7100 comes in both 32 and 64-bit flavors and is about 2.35 gb in size (for the 32-bit version - I don't know if the 64-bit version is any bigger or smaller).
You'll need to have a Windows Live account (free to sign up) and a valid e-mail address to get to your download page (which will have the serial key to activate your version of Windows 7).
For the current Beta users out there: don't worry about having to install build 7100 immediately. Microsoft announced that "the RC will be available at least through July, and we're not limiting the number of downloads or product keys" (RC download page) and that "the Beta expires on August 1, 2009, and bi-hourly shutdowns will begin July 1, 2009. The RC will expire June 1, 2010, and the bi-hourly shutdowns will begin on March 1, 2010" (RC download page).
I just downloaded and burned the new OS to DVD this afternoon and I plan on installing it sometime this weekend (too much schoolwork to get it done during the week, but I'll be sure to include plenty of pictures/my thoughts when I get around to installing it).