I'm sure there are plenty of people aware of this, and I'm sure it's been posted somewhere else.
Microsoft has released a customer preview of Windows Vista Beta 2.
Essentially, you sign up with a valid e-mail address, and they give you a product key for Vista Beta 2 good until June 2007 (I think?) for 10 computers, and then you get to download it or order a CD.
I tried downloading it today, but it seems their server is swamped. However, I've already tried out the Developer beta release (without activating it), so I know it's already neat. As soon as their server's better, I'm definitely downloading it. If nothing else, it's a way to get a computer with a legal copy of Windows for a year.