Google OpenID Federated Login API has been extended to Google Apps, that’ll allow users to sign in to third party websites using their Google Apps account, without sharing their credentials with third parties. In addition, Google Apps can now become an identity hub for multiple SaaS providers, simplifying identity management for organizations. For e.g., when integrated with partner solutions such as PingConnect, the Google Open ID Federated Login API enables a single Google Apps login to help provide secure access to services like Salesforce.com, SuccessFactors, and WebEX — as well as B2B partners, internal applications, and of course consumer web sites. See Ping Identity's post and demo.
More info: Code Blog