Google Data Authentication

Google Data Authentication - Start Here
Getting Started with Account Authorization
Authentication in the Google Data Protocol
OAuth
OAuth in the Google Data Protocol Client Libraries
OAuth for Web Applications
OAuth for Installed Applications
OAuth API Reference
Using OAuth with the Google Data APIs
Google Data API Tips - OAuth
OAuth Playground
OAuth-enabled http test client: oacurl
Gadgets
Authentication for Gadgets
Writing OAuth Gadgets
Fetching Remote Content
Creating a Google Data Gadget
JavaScript client library API reference
Using JSON with Google Data APIs
OAuth Enabled Gadgets on OpenSocial enabled Social Networks
Registration
Registration for Web-Based Applications
OpenID
Federated Login Service for Google Apps
OpenID+OAuth
Sharing and previewing Google Docs in Socialwok: Google Data APIs
Step2 Code Project
OpenID OAuth Extension
ClientLogin
ClientLogin in the Google Data Protocol Client Libraries
ClientLogin for Installed Applications
Google Data API Blog - ClientLogin
AuthSub
AuthSub Authentication for Web Applications
Using AuthSub in the Google Data Protocol JavaScript Client Library
Google Data API Tips - AuthSub

Google I/O
OpenID-based single sign on and OAuth data access for Google Apps

By Jeff Morgan, Senior Technical Consultant at Appirio