[AnneTheAgile]

The open source implementation, Rietveld [ http://code.google.com/p/rietveld ], sounds very interesting. Perhaps it could be used in programming classes and might also fit in with pair programming training.

[sandGorgon]

does using Rietveld mean that one has to use the app-engine ?

[dlsspy]

gerrit was originally a port of rietveld for git, but is its own thing now. You run it on your own machine.