here is my research on detecting communities in Twitter's Social Graph (36 Million users) using Label Propagation algorithm. http://www.akshaybhat.com/LPMR/
You can find both code as well as results.
Also, thanks for releasing your code. I'm currently working with the Junto package http://code.google.com/p/junto/ but I'll give your map reduce implementation a try for the added benefit of running LP on larger datasets.
If you dont have access to a Hadoop cluster, I have some multiprocessor code, which is slightly faster, if you have enough RAM (32 Gb for twitter dataset). drop me mail if you need it.