Google offers the Analytics Management library with .NET development in mind. Access resources using either an API Key or OAuth 2.0. To start using the library, study the examples for web applications, service applications, and installed applications. Additional to Analytics Management, this .NET library can be used to interact with more APIs. Choose from an extended list at https://developers.google.com/api-client-library/dotnet/apis/
AlchemyAPI this week exposed a computer vision API to extend its text analytics cloud service in a way that will make it easier for publishers to identify images that are closely related to one another.
We have seen an explosion in the number of APIs that are now available to developers. It seems like almost everyone has one and those that don't are scrambling to get one. The focus now is clearly not on just having an API, but having a "great API." Two excellent presentations from Cloudstock, held earlier this month, give you an overview on the current state of the API market and tips on what makes a great API.