Google :
https://www.googleapis.com/oauth2/v3/userinfo?access_token={0}
Twitter :
- Twitter does not expose an endpoint that provides the user's email address. Not even the profile endpoint. Below is an extract from the Twitter's FAQs page...
If you'd like a user's email address, you'll need to ask a user for it within the confines of your own application and service. The Twitter API does not provide the user's email address as part of the OAuth token negotiation process nor does it offer other means to obtain it.
Yahoo :
I don't think it exposes the user's email address either. Yet, the endpoint to retrieve the user's profile is...
You can find more info here. http://developer.yahoo.com/social/rest_api_guide/extended-profile-resource.html