"Contextual rule-based text normalization engine written in java, that can be used to implement stemming algorithms or phonetic normalizers. The project includes a french stemmer/phonetic normalizer, and a soundex implementation. Includes a Lucene Analyzer"
Nutch (http://www.nutch.org/) is a web search engine that uses Lucene as it's search technology.
It adds a scalable crawler, link database, distributed searching, and a web-based search interface.
Luke (http://www.getopt.org/luke/), Lucene index browser.
CodeCrawler (http://codecrawler.sourceforge.net/), is a smart web-based search engine specifically built for use by developers for searching source code that uses Lucene.
RealtimeSearch (http://issues.apache.org/jira/browse/LUCENE-1313) provides realtime search using Lucene.