I'm currently playing with the awesome Apache Solr, and preparing to install it on my production server. Here are a few links I've found that I believe have good value.
First, there's the code you'll need to make it work:
The a few tutorials on setting things up:
Installing Java 1.6 on MediaTemple dedicated virtual server (dv)
http://www.jaysonjc.com/2008/01/13/installing-java-16-jdk60-on-mediatemp...
Setting up Apache Solr
http://lucene.apache.org/solr/tutorial.html
Setting up the Apache Solr Drupal Module
http://drupalcode.org/viewvc/drupal/contributions/modules/apachesolr/REA...
Some more help guides:
http://drupal.org/node/343467
Customising things:
http://drupal.org/node/598970
http://drupal.org/node/230412
http://drupal.org/node/401234
http://drupal.org/node/504804
http://www.brightlemon.com/knowledge-base/blog/customizing-apache-solr-s...
http://drupal.org/node/492250
Setting Apache Solr up as a service so it automatically starts
http://drupal.org/node/507292
Drupal Apache Solr Search Multi Site Setup
http://www.anovasolutions.com/content/drupal-apache-solr-search-multi-si...
Dont' have a dedicated server? No worries, Acquia sell a hosted Apache Solr Solution!
http://acquia.com/products-services/acquia-search
And out of left field, a few interesting Drupal bits:
http://drupal.org/node/492494
http://drupal.org/node/201594
