It's available on MSDN now if you have a subscription. Otherwise I think you have to wait till Friday, and it will be available here: http://www.microsoft.com/windows7
Basically it's the full MSDN for 3 years. It also includes hosting deals for the server products. At the _end_ of the 3 years you have to pay $100. Overall pretty sweet if you're using the MSFT stack or need the OS's for testing.
If you're a Stirr member they can connect you - there are also other partners you can find on the bizspark site.