eDoogle for Gnutella?
 

Cool, check this out http://edoogle.dyndns.org:8080/
I think you could do this on Gnutella, what do you think?
It searches the ENTIRE network, but uses a cache system to keep bandwidth low, and if everyone used this to find files you would have less search queries on the network!

Well there was a tracker like this.
But somehow its not there anymore,
the url of it was: www.gnufrog.com