MLTK is a collection of machine learning algorithms in Java, supporting Generalized Linear Models: Ridge, Lasso, Elastic Net, Regression Trees, Random Forests, and more. Free download under BSD license.
Spark solves similar problems as Hadoop MapReduce does but with a fast in-memory approach and a clean functional style API. Leveraging Hadoop Yarn, Alpine has made it very simple to get started with Spark.
Prediction.io is an open source machine learning server for predictive solutions, such as personalization or recommendations, built on top of scalable frameworks such as Hadoop and Cascading - ready to handle Big Data.