Lucene implementations in languages other than Java:
CLucene - Lucene implementation in C++
Lucene.Net - Lucene implementation in .NET
Lucene4c - Lucene implementation in C
LuceneKit - Lucene implementation in Objective-C (Cocoa/GNUstep support)
Lupy - Lucene implementation in Python (RETIRED)
NLucene - another Lucene implementation in .NET (out of date)
Zend Search - Lucene implementation in the Zend Framework for PHP 5
Plucene - Lucene implementation in Perl
KinoSearch - a new Lucene implementation in Perl
PyLucene - GCJ-compiled version of Java Lucene integrated with Python
MUTIS - Lucene implementation in Delphi
Ferret - Lucene implementation in Ruby
Montezuma - Lucene implementation in Common Lisp