Open source search tools: ht://dig and swish-e
DelphiFAQ currently uses swish-e for searching documents. The presentation of the results is home-made.
I had used swish-e several years ago, and switched then to ht://dig. ht://dig is a great tool, but I could not get it to work on my new web host's environment. (I had to move from OLM to bluehost because of OLM's intolerable outages in 2005 and early 2006.)
For a while I ran the search function on the (frequently inavailable) old box -hosted by OLM- until I put in the time to migrate it completely to BlueHost, now implementing swish-e again.
The crawler runs currently not on a fixed schedule. Instead I manually start the crawl process. I am still looking into optimizing the recrawl process. I start the crawler about every 2 or 3 days. This means that if you run a search on a string that appears in a very recent comment, then this string may not be found yet.
You are welcome to leave feedback on the search function here.