Someone mentioned a peer to peer search engine in a support thread and I've taken a look at it. Seems to be pretty clever. It seems like the limiting factor at the moment might be the number of nodes in the network. Anyone else interested in taking look and running a peer on their server?
Here's a quick overview: http://yacy.net/en/Philosophy.html
and there's a download on their homepage. It's dead easy to set up as well. And after running for a short period of time I'm already starting to see reasonable results for popular topics.