Looking for open source projects in java and python

I would say openrdf sesame in the java world can use hand. It is one of the most widely used RDF and SPARQL apis on the java side. Very useful, when dealing with data from many sources without building a single datawarehouse.

I'm working on this one, you might be interested. http://archesproject.org/ It is implemented on Django Framework on python.

I would highly recommend getting involved somehow with IPython. It's a great platform and not a bad codebase, and yields some pretty cool stuff!

pandas (python data analysis library): https://github.com/pydata/pandas (friendly/helpful devs and easy to contribute)