Most participants who come in for an API study on Avalon ask me where they can get access to the bits so that they can use Avalon at home. Up until now I've always had to tell them that they could only get access if they were MSDN subscribers. That is now no longer the case - the Avalon team has just released the November CTP release to everybody, MSDN subscribers and non-subscribers alike.
You can use the freely available beta release of the VS Express Products to build Avalon applications.
Once you've had a look at Avalon, sign up for a usability study so that you can come in and give us your feeback!