IR packages

So I mentioned the Lucene project last time.

Andrew McCallum (UMass) still makes the
Bag of Words software available.

What other packages are available to those who want to build their own IR systems? They may or may not support multiple languages or multiple retrieval models. They may be general purpose, or perhaps restricted to Web search for example.

The Lemur package from CMU

Two packages from NIST
PRISE
NIRVE

References to these and a couple more can be found at the
SIGIR site. There's some good stuff out here!

MG is a little older, and is discussed in detail in the book Managing Gigabytes. Zettair is related to MG, I think.