Don Box has a great article on MSDN for starters. As I mentioned earlier, Indigo got release at the PDC in LA in October.

Our home on MSDN is http://msdn.microsoft.com/webservices

Also, check out the Longhorn page for more articles on Indigo; slides from the PDC, and on other major technologies that Microsoft showcased at the PDC - WinFX, Avalon.

Download location:

http://msdn.microsoft.com/events/pdc/after/default.aspx#longhorn