Single Sign-On for Integrated Open-Source Apps?

maiden_taiwan asks: "We're constructing a free groupware application by integrating well-known open source components: apache webserver, inn news server, ircd chat, scp for file transfer, etc. Unfortunately, each app has its own incompatible concept of a 'user identity.' Apache has the htpasswd module, IRC has nicknames, scp has public keys, NetNews has the poster's email address, and so forth. Has anyone managed to integrate a similar suite of apps using a single sign-on model, where a user has a single identity that is understood and carried through all these apps?"