Beyond creating a manual listing which is easy to read frmom a web page but gets out of date pretty quickly, maybe we could consider a dynamic advertisement mechanism like ZeroConf:
http://en.wikipedia.org/wiki/Zero-configuration_networking
This would be analogous to what RIP is doing for the AMPR routes but for services. Remote machines would then advertise their available services via Avahi for Linux, Bonjour for OSX, etc. There is also SSDP for WIndows that does a similar function which is supported by many SOHO routers as well.
--David