<p>I'm looking to find alternatives to <a href="http://lucene.apache.org/solr/" rel="noreferrer">Solr</a> from the Apache Software Foundation. </p>

<p>For those that don't know, Solr is an enterprise search server. A client application uses a web-services like interface to submit documents for indexing and also to perform search queries. Solr has other features built in like caching and replication. I believe it was originally started by CNet and then open-sourced. </p>

<p>I'm looking for other search servers out there that might be seen as the competition. </p>

IBM Omnifind Yahoo Edition
is an Enterprise search server which uses
Apache Lucene
for indexing. It is simple, easy to install and administer. It also has a built in Open Search API. It has multi-platform support and its Free!!
This product was launched by IBM to compete with
Google Mini
in the Enterprise Search market.