Bixo is an open source web mining toolkit that runs as a series of Cascading pipes on top of Hadoop. By building a customized Cascading pipe assembly, you can quickly create specialized web mining applications that are optimized for a particular use case.

Take a look at the Getting Started page, and also the list of resources (mailing list, bug database, source code, etc)

Bixo is an open source project released under the MIT License.