This page will be a jumping off point for SolR and Nutch. It will point to other pages which describe how Nutch interacts with SolR.
SolR is a full text search server using the Lucene Java libraries. In fact it is a sub project of Lucene to be found at http://lucene.apache.org/solr/
SolR Wiki (but they may not know about Nutch, of course)
http://groups.drupal.org/lucene-nutch-and-solr - A forum for people who use Nutch and SolR together with Drupal - a PHP Content Management System