If you are serious about Drupal search, then you are probably aware of the fantastic integration between Drupal and Apache Solr - the open source search server based on the Apache Lucene search library. The Apache Solr Integration module offers some very straightforward instructions on replacing the core Drupal search with Apache Solr (the same search server that powers drupal.org and www.whitehouse.gov).  And in replacing core search, the Apache Solr Integration module devlivers pretty much exactly what you would want and expect, such as:

1. Faceted search
2. Replacing taxonomy pages with Solr search
3. Result biasing
4. Content biasing and exclusion
5. The list goes on and on...

But what happens when your requirements are a bit more complicated than just replacing core search?  

Many of my clients have been through several iterations of improvements and refinements to their enterprise portal / corporate intranet environments to include portal personalization and customization, improved content management integration and content authoring, and basic search.  In fact these features are now considered to be “Phase One” items on new implementations as well.

What is emerging now is the expansion of these portals / intranets to include a truly integrated enterprise search.  Vendors such as Vivisimo (Velocity), Google (Google Search Appliance), and Microsoft (FAST) provide search engines that provide an extended reach beyond portal and content managed information to include data from enterprise systems such as PeopleSoft, SAP, and Cognos, etc.  These systems can be searched via vendor specific connector technologies, which is typically accomplished through a customized API and an extension to an organization's services tier.  These search vendors also provide information optimization capabilities such as faceted results (categories), user tagging, and relevance rating, etc.