We have just published two new search providers: an Indexing Service search provider and a Lucene provider.

Indexing Service is an operating system component and doesn't require a lot of additional administration, but requires administrative privileges on the Windows box and is difficult to use in a shared hosting scenario.
Apache Lucene is an open-source, high-performance, full-featured text search engine library. It is a technology suitable for nearly any application that requires full-text search. It allows you to have greater control over the indexing process and to even use "pre-generated" indexes. Lucene search provider doesn't rely on the system services and other background tasks.