We just released the December 2007 CTP of Project Astoria, or I guess I should say the ADO.NET Data Services framework as Mike pointed out.
This is an important milestone for Astoria, as this is the first release that is based on the real, production code base and not on the initial prototype that we built to explore the space. Formats, APIs, URLs and other interface elements have been extensively revisited so I would recommend that you switch to the new CTP for any future work.
This CTP is compatible with the RTM version of Visual Studio 2008, so you can finally move off intermediate builds of it when working with Astoria.
We're looking forward to hearing your thoughts on this new CTP!