You haven't written anything about your interest. I know algorithms in graph mining has been implemented over the Hadoop framework. This software http://www.cs.cmu.edu/~pegasus/ and paper: "PEGASUS: A Peta-Scale Graph Mining System - Implementation and Observations" may give you a starting point.
There was a NIPS 2009 workshop on the similar topic "Large-Scale Machine Learning: Parallelism and Massive Datasets". You can browse some of the paper and get an idea.
Edit : Also there is Apache Mahout http://mahout.apache.org/ -->" Our core algorithms for clustering, classification and batch based collaborative filtering are implemented on top of Apache Hadoop using the map/reduce paradigm"