Where can I find a list of scopes for Google's OAuth 2.0 API?

What you are looking for is the Google APIs Discovery Service.

A few other interesting resources:

• An excellent blog by Nicolas Garnier which describes the important things behind this service.

• The Google OAuth2 playground, is another good source of info.

• Finally if you're interested in tracking changes to the discovery documents or don't want to read all the docs, there is an interesting online implementation by Gerwin Sturm.

Thanks to Antonio Sacco's links, I was able to find:

https://www.googleapis.com/discovery/v1/apis/oauth2/v2/rest?fields=auth(oauth2(scopes))

It says these are the scopes available:

 - https://www.googleapis.com/auth/plus.me (Know who you are on Google)
 - https://www.googleapis.com/auth/userinfo.email (View your email address)
 - https://www.googleapis.com/auth/userinfo.profile (View basic information about your account)

Here is a doc that was added recently to Google's OAuth 2.0 documentation, with a comprehensive list of scopes:

https://developers.google.com/identity/protocols/googlescopes