The July 2010 Release (build 22.214.171.1240) July 2010 Second Release (build 126.96.36.1991) is live: http://mfcmapi.codeplex.com.
The scope of this release was primarily under the covers engineering, most notably to add SAL annotations. While adding these notations took seemingly forever, in the process I did run across a few potential crashing bugs, so the effort was worth it. It should pay off even more going forward.
Here's a change list - see the Issue Tracker on Codeplex for more details, or look at the code:
[Edit, 7/27/2010: Added details about 188.8.131.521]