You can get the November Orcas extensions for VS 2005 here:
They are a CTP however they have been very stable and have not caused any problems for us at all. All the November CTP does is allow you to create/open WPF projects, it shows the beginnings of the Cider designer (which was very buggy back at that time and we don't recommend using it) and gives some Intellisense in the XML editor for XAML.
You do need either those extensions OR a CTP Virtual PC of the latest Orcas builds. For most people the extensions are the way to go until the final version of VS Orcas comes out in a few months.
We've added this info to a Troubleshooting documentation topic in the next build of Ribbon.
Look for the next Ribbon build probably Monday... it's going to have some really big new features.