Personally I use CDEX http://www.cdex.n3.net/ you can download a copy from their site.

In terms of alternative uses for gnutella you should consider file distribution because currently the demand for content is overwhelming and there simply isn't a lot of people doing solid sharing.

I assume this is due to legal concerns as people may not be willing to leave their hosts running for long periods of time fearing legal action by the many companies monitoring activity on the Gnutella network looking for illegally shared content.

Hope this helps.

http://www.leeware.com