Can I use OAuth (and not other services) to fetch the user's picture, gender, location and email address from google?

I'm currently using the following API : http://www-opensocial.googleusercontent.com/api/people/@me/@self

and scope is: http://www-opensocial.googleusercontent.com/api/people/

Here is a list of all Services, that Google provides access to via OAuth: http://code.google.com/apis/gdata/docs/directory.html

You could use the Google Apps Api from there, if all your users have Google Apps accounts.

But I guess they don't have. Unfortunately I don't know of any other API, that provides access to the user himselfe, you can however use the contacts Api, which will provide you the information (gender, location, email, ...) about the users contacts..