Google has evolved their API authentication to embrace OAuth 2.0.
Even though the OAuth 2.0 specification isn't 100% finalized, Google has overhauled all of their APIs in Google Code to support it.
OAuth 2.0 is much easier for developers to implement, and simplifies OAuth consent for application users.
Google's support for OAuth 2.0 is a big boost for developers integrating with their API, as well as big vote of support for the future of OAuth 2.0 as the standard for API authentication.
You can find documentation for OAuth 2.0 underAuthentication and Authorization for Google APIs.
