indexing services for websites: lucene, and other options

Just looking for some search and indexing services for our sites, and wondered if you guys could recommend anything?

our requirements:

• The service can either index via http, or direct access to our database.
• It's gotta be just really simple to use, and set up
• provide a simple API so we can get the results programmatically and do what we want with it
• ideally free, or very cheap

so far we've looked at Yahoo Boss and Lucene. Any pros, cons, or opinions for those?

Lucene's looking good. We're a .NET house so LINQ to Luncene looks cool, and of course the .NET port Lucene.NET. But by all means, it can be any technology.

Cool, thanks for your help!

I would recommend Solr. Lucene technology, but server-side.