Grant Ingersoll has been working on search and natural language processing for about ten years. He is an Apache Lucene and Solr committer as well as a co-founder for Lucid Imagniation, which is focused on commercializing those two projects. Lucene is a Java library for building search applications and Solr provides a layer over Lucene that gives developers the tools they need to put Lucene into production. Ingersoll says you should think of Lucene as the engine, and Solr as the car.
Ingersoll says the pace of development in Lucene and Solr has been very exciting over the last few months. Right now there's a lot of work on spatial/geolocation capabilities. Also, more flexibility is being added to scoring search relevance and indexing. Ingersoll is currently working on a book that provides solutions for many text-based problems in search, categorization, natural language processing, and machine learning.