Carrot2 is an open source framework for building search clustering engines. This is the framework used by grokker.com from which Dr. Calvo suggested I look into.
My current understanding of the framework is that it is a package of components:
1. Input components (interfacing between search engines, etc)
2. Filtering components (using clustering algorithms to obtain clusters of results)
A picture taken from the Carrot2 Project website sums up the overall structure of the framework: