[iamveen]

I have yet to use this for anything, so I can't vouch for it's quality, but it seems to be exactly what you are looking for.

http://www.keycloak.org/

Website blurb:

Add authentication to applications and secure services with minimum fuss. No need to deal with storing users or authenticating users. It's all available out of the box.

You'll even get advanced features such as User Federation, Identity Brokering and Social Login.