Shibboleth is a 'single-sign in', or logging-in system for computer networks and the internet. It allows people to sign in, using just one 'identity', to various systems run by 'federations' of different organizations or institutions.
Since Shibboleth supports
SAML 2.0, it is possible to integrate it with SharePoint 2010. In the nut-shell:
CONFIGURE SHIBBOLETH 2 AS CLAIMS PROVIDER FOR AD FS 2.0
CONFIGURE SHAREPOINT 2010 AS A RELYING PARTY FOR AD FS 2.0
I am not going to re-invent the whole wheel here. There is a detailed white-paper explaining how this can be setup. I will share the link to access that.