My company will be soon switching to Google Apps, and I would like to propose the idea of having our site administration page being authenticated with OpenID. Therefore, any user who is logged into Google Apps would be automatically logged in to our site Administration. Currently, our site administration has it's own list of users and passwords in the DB, but I would like to have the user list based off Google Apps, with their unique identifier saved in our DB. That way, new employees would only have to be set up in Google Apps to access our site Administration.
I've done some research, and come across terms like SSO, OpenID, and SAML, but I can't quite narrow down which route I'm supposed to go. It seems like Google has a lot of paths open for development, and I'm not sure which one I'm supposed to take.
My question is: What kind of Authentication am I seeking for my purpose described above, and can anyone point me in the direction of where to get started? My site is published in ColdFusion 9, so answers specific to that platform are a bonus.
If you just need Web SSO -- I believe you would use your GApps domain as an OpenID Provider. Your application would then act as an RP and consume identities as established by your own GApps domain and company administration. GApps can only act as a SAML Service Provider -- so using SAML for this use case isn't realistic.