Infrastructure Team/Central Login

Summary

This is initiative to permit a user to access multiple SL resources while providing their credentials (such as userid and password) only once.

Single sign-on on all Sugar Labs services, and, in theory, on any Sugar related sites that want to get benefits from Sugar Central Login (there is no need to be hosted on Sugar Labs servers or so, only authentication will happen in centralized manner).
Centralized users database.
Reuse users database not only for Web services, but also for shell account, for example.

CAS, the most common method, with a requirement to provide login/password, is useful for people who are not arriving from a Sugar Shell instance (and so, Sugar's certificate-based method does not work implicitly for them), and for casual visitors or those wishing to avoid the technical work of taking care of user side certificates. The full featured option.
OpenID authentication. Would be useful if particular service can link OpenID users and the ones got from CAS/LDAP. Without that, OpenID is just a standalone authentication method for particular service that does not relate to Central Login at all.
Users certificates. Might be useful, e.g., for people who need to be authenticated from a Sugar Shell where Sugar might perform some authentication routines under the hood.
Any method that can process authentication via LDAP, to reuse centralized users database only (no single sing-on).