Authentication and Authorization for Google APIs - Google Code
API Documentation | foursquare Developers Start by registering your app to obtain its foursquare API credentials. Be sure to use an account with a secure password to own these credentials. If you're creating an app on the behalf of a full-fledged company, consider creating the key in association with the page account for your company. Since each set of credentials is tied to a particular URL, you may want to create different credentials for your development server and production server. For the purposes of OAuth, your “key” from that registration process is your “client id” here, and your secret from registering is your secret here. Access tokens allow apps to make requests to foursquare on the behalf of a user.
Connect with Viadeo | Viadeo API
Sign in with Twitter Updated on Wed, 2012-09-26 11:20 Place a button on your site or application which allows Twitter users to enjoy the benefits of a registered user account in as little as one click. Works on websites, iOS, mobile and desktop applications. Features Ease of use - A new visitor to your site only has to click two buttons in order to sign in for the first time.