Reader Digerati offers detailed instructions for getting your Windows 7 beta product key which worked for me (when many of the other tactics people are trying around the Web did not). Here's what you do.
Step 1: Log onto [technet.microsoft.com]by clicking on "Sign in" in the upper right corner with your Microsoft Passport ID. (i.e.: Hotmail, etc.)
Step 2: Copy (don't CLICK!) one of the links below to the address bar and press Enter.
32-Bit key: [www.microsoft.com](Copy and Paste!)
64-bit key: [www.microsoft.com](Copy and Paste!)
Tip: You can use the 64-bit during a 32-bit installation and a 32-bit key during a 64-bit installation. (It seems that getting a 64-bit key is faster!)
Step 3: If you receive an error, just press CTRL+ F5 (non-cache reload) to refresh. (I had to refresh more than 10 times before I received the key), if you're being redirected then you didn't follow the steps 1 and 2 correctly!
If you followed the steps correct you should see your key (depending on your version it could also say Windows 7 Beta 32-bit Product Key).
Thanks, Digerati! This worked for me on the first try. Let us know if that works for you in the comments.