Lucene is a wonderful thing
Erik has been doing some fascinating work with us at the University of Virginia where we use Lucene to index The Rossetti Archive, a comprehensive digital edition of Dante Gabriel Rossetti's works. He transformed our search engine from a sloth to a cheetah. Searches that used to take minutes finish in under a second with Lucene.
I can't say good enough things about the Lucene technology or Erik's expertise with it. If you work with data and need to find it, Lucene may be of interest to you.