http://middleware.internet2.edu/shibboleth/
Interesting project for you security/privacy control
freaks out there...
"Shibboleth, a project of Internet2/MACE, is developing
architectures, policy structures, practical technologies,
and an open source implementation to support
inter-institutional sharing of web resources subject to
access controls. In addition, Shibboleth will develop a
policy framework that will allow inter-operation within
the higher education community."