Apache Hama
I came to know Apache Hama back in 2010 when I was looking for a robust Java framework for running parallel algorithms for doing matrix multiplications for very huge matrixes. From then on I followed the project but kept silent for a while on the mailing lists just trying to understand what the project status was and also if/how BSP based algorithms could be the right fit for my use cases.
I then joined in as a mentor on March 2011 because the project was lacking of active mentors able to give help on the community empowering and on the release process.
Now I am a very passionate user and developer (I used it in a production system for doing parallel exports/imports from MongoDB to Apache Solr). It's nice to see the community has grown incredibly in the last year therefore I'm a bit proud about the project having become a TLP.
I'm working now with Apache Hama especially for machine learning tasks and that's the area my latest contributions belong.