Anyone else working on this, or have suggestions for how to go about it?
The simplest solution would be to use MySQL's built-in full-text searching, but it seems kind of primitive. No multiword patterns, no ability to match words with punctuation ("C++", "2.5.1", etc), no regexps, etc.
Alternately I've used Glimpse in the past (six years ago!), and it was pretty fast and powerful. However, it's not free software. Also, since it expects to be indexing files rather than database entries, it'd take a little more hacking to hook into it.
What other search engines - especially free one - have people worked with?