Dave Balmain has ported Lucene to Ruby, using a C extension to improve the speed so that it's as fast as Java Lucene (at least for indexing). The Ferret site is down at the moment [cache], but you can download v0.9.4 from RubyForge to compile yourself and read sample code, or install with gem install ferret. There's also an acts_as_ferret plugin for Rails (that can be integrated into Typo), and Ferret discussion as a mailing list or forum.
I haven't properly tested Ferret yet to see if it handles all the edge cases as well as Java Lucene or PyLucene, but it seemed to work ok on a basic test case.
