I put together a chm file for the Orcas Microsoft.TeamFoundation.Build.Client and Microsoft.TeamFoundation.Build.Common namespaces the other day using Sandcastle and the invaluable Sandcastle Help File Builder, so here it is. Please keep in mind that this is preliminary documentation, everything is subject to change before RTM, etc.
We'd love to hear what you think of the Orcas Team Build features, including the Object Model, so please download Beta 1, check out these docs, and post any comments/question/concerns you might have.
Note: attachment removed. Please grab the Beta 2 documentation instead.