Not sure if you noticed but there is currently a LARGE effort around MVVM Light documentation. On one hand the Pluralsight course I have been working on for the past months is in the final stages of review now. Also, I have revamped and actualized the MVVM Light pages on my site as well as the Documentation page on Codeplex.
One thing that was still on my list is to publish the source code documentation. You might know that (or not), but the MVVM Light source code is documented in a pretty complete manner with XML documentation. There are here and there comments that are missing or incomplete, but for the most part it is pretty solid.
In order to make the usage of this inline documentation easier, I extracted it using Sandcastle. The source code documentation is now available as CHM (compiled HTML) documents as well as online HTML at the following location.