If you're interested in downloading (and getting a beta key for) Windows 7, you better hurry because time is running out. Just head on over to the Win7 Beta page
and pick between 32 or 64 bit, or go for both.
What makes Windows 7 so awesome? Oh, just a really nice performance boost, improved taskbar, Jump Lists, Federated Search, better device management, new hotkeys and UI elements, and the incredible new HomeGroup feature to start with. Read more here