How do I implement Search Functionality in a website?This my Answer to the stackoverflow question: How do I implement Search Functionality in a website?:
It depends on how comprehensive your web site is and how much you want to do yourself.
If you run a medium site with an sql engine use the search features of your sql engine.
If you want to abstract your search from your application and be able to query it in a language neutral way with XML/HTTP and JSON APIs, have a look at solr. Solr runs lucene in the background, but adds a nice web interface to it.