One of the Code for America Accelerator companies is Revelstone Labs and does performance mgmt for local gob
I wouldn't necessarily look at other government agencies. I don't think that anyone has really tackled performance management effectively. I would look at social performance management systems like Salesforce's system (previously Rypple). We need to completely re-engineer the performance management process. Goals should be "social," feedback should be continuous and from many sources. Performance management needs to be integrated with your talent management solution and be an on-going process.
Assuming you are looking at government, I would encourage you to read the National Performance Management Advisory Commission's report on the subject at http://pmcommission.org. Although it may not reflect all of the real-life difficulties in implementing the various elements of performance management practices,it provides a good summary of the appraoches and concepts that are important for performance management to impact our results.