Slightly OT: site search engines

[Ian M. Evans]

I'm currently using Google Custom Search for our site search, but I'm 
not entirely happy that it doesn't always find pages on our site that 
can be found using Google.com. Perhaps I'm hitting a page limit wall.

Just wondering what you guys are using for search on your sites. I'd 
really like to find something that's open source and plays well with 
nginx and php.

Any ideas?