Microsoft really wasn't kidding when it said the first Windows 7 release candidate would become available to the public on May 5. The public RC download is already up right now—all you need to do is sign up with a Windows Live ID and fill in a short form.
Once the form is filled out, you'll get your product key and a download link. Downloading means using a Java or ActiveX download manager, which seems to be a tad finicky. (Attempting to resume the download a bunch of times did the trick in my case.)
The RC comes in the form of a DVD image, which weighs in at 2.36GB for 32-bit systems and 3.05GB in its 64-bit iteration. If you're not versed in the arts of DVD burning, you'll need a DVD writer and software like Nero or InfraRecorder to get the image on a disc—either that, or just use your virtual machine of choice to bypass physical media entirely.
Microsoft notes that the RC will continue to be available publicly "at least through July 2009." The firm won't put a cap on key distribution, so everyone should have plenty of time to take a gander at the new operating system. The RC will keep working well after Windows 7 hits stores, too. Microsoft tells testers to expect bi-hourly reboots every two hours starting on March 1, 2010, with final expiration due on June 1, 2010. (The latest reports suggest the final version of Windows 7 will be out in late October.)
If you're already using the beta and are wondering whether you should make the jump, Microsoft has detailed all of the changes in the new release in two blog posts: Some Changes Since Beta for the RC and A few more changes from Beta to RC. Generally speaking, you can look forward to bug fixes and improvements to the taskbar, Aero Peek, touch features, and Windows Media Player.