I am happy to mention that Medsphere has received certification for their OpenVistA EHR system.
As far as I know, this is the only meaningful use certification for Open Source software, for the in-patient setting. All of the other certifications that I have mentioned so far have been ambulatory.
Congratulations to the Medsphere team. This is an important accomplishment, and a milestone for the Open Source health software community.
-FT