The ASF is made up of more than 150 top level projects which cover a wide range of technologies. Chances are if you are looking for a rewarding experience in Open Source, you are going to find it here.
Commons CLI provides a simple API for presenting, proecessing and validating a command line interface.
Scalable machine learning library
Client-side HTTP implementation in Java.
Commons HttpClient is a library for client-side HTTP communication. It provides support for HTTP/1.1 and HTTP/1.0, plus various authentication schemes and cookie policies. Thanks to it's widespread use and years of development, it is a very mature and stable codebase. However, due to limitations in the API design, Commons HttpClient will eventually be replaced by HttpClient 4.0 with a completely redesigned API based on HttpCore.