Wouldn't an Avalon / XAML emulator be great? Kinda like the PocketPC emulator that's part of the MS Embeded Visual Toolkit. Then those of us who didn't get to PDC, don't have Longhorn, but would love to start working with XAML could at least start getting acquainted with it.
Of course Avalon is a huge project that supports some pretty complex capabilities, but I'd like to try just throwing some buttons on forms and getting my first Hello World going. Since it's XML based, it would seem like a rough emulator could be built with some XSL to build an ASPX HTML page with System.Web.UI or even .NET (I mean WinFX) UI components, right? I'm probably missing something that makes this more complex.
I guess there's another option - buy the PDC disks and find a spare computer to install Longhorn.
Update: Quoth DonXML “We (the SharpVectors team) are going to try to update our open source SVG .Net rendering engine to be able to handle XAML. If anyone would like to lend a hand please contact me.” Woo hoo!