Widget Standards
OpenID
OpenID is a decentralized identity service base on open standards that allows users to log on to many different sites using a single digital identity. This would greatly simplify the creation of mashups that require authentication. At the same time, OpenID challenges how educational institutions handle identity:
OpenSocial
OpenSocial is a initiative lead by Google to create a set of APIs for accessing social network data and core functions from social network sites and using these in web applications. It is often described as a more open cross-platform alternative to Facebook. Ideally, users could export the social graph from one site and bring it to another. Open Service Interface Definitions
Open Service Interfaces Definitions (OSIDs) are standards for systems interoperability that are central to the mission of the Open Knowledge Initiative of making it easier for educational institutions to develop and share resources. For example the Repository OSID specifies how one system, an OSID consumer, can access and use assets from another remote system, an OSID provider. Universal Widget

It should be noted that W3C is working on a widget standard, see: Widgets 1.0: Requirements
OAuth
OAuth allows you the User to grant access to your private resources on one site (which is called the Service Provider), to another site (called Consumer, not to be confused with you, the User). While OpenID is all about using a single identity to sign into many sites, OAuth is about giving access to your stuff without sharing your identity at all (or its secret parts).