Contextual ad script
 

Anyone got any recommendations?

Any ready-made solutions? I can always get it custom but an existing solution would be better for my current purposes.

I don't know of any, sorry. A keyword density script might help for your needs?

A Hotscripts.com search for 'contextual' brought this site up. They seem to be selling commercial contextual ad server software.
http://www.w3matter.com/

Thanks, Brujah. This might be it. I've heard there's one that exists that a lot of people are using but it has database efficiency issues. Thanks for the lead, I'll check up on it.