Supported providers

Provider Protocol Dev. network / App. registration Notes
AOL OpenID -
Disqus OAuth 2 https://disqus.com/api/applications/
Dribbble OAuth 2 https://dribbble.com/account/applications
Facebook OAuth 2 https://developers.facebook.com/apps
Foursquare OAuth 2 https://www.foursquare.com/oauth/
Freeagent OAuth 2
GitHub OAuth 2 https://github.com/settings/applications
Google OAuth 2 https://console.developers.google.com
Instagram OAuth 2 http://instagr.am/developer/
Mailru OAuth 2 http://api.mail.ru/
Odnoklassniki OAuth 2 http://dev.odnoklassniki.ru/
OpenID OpenID -
PaypalOpenID OpenID -
Px500 OAuth 2 http://developers.500px.com/
Reddit OAuth 2 https://ssl.reddit.com/prefs/apps
Stackoverflow OpenID -
Steam OpenID http://steamcommunity.com/dev/apikey Steam does use OpenID to authenticate their users, however they use a proprietary API to retrieve the user data which need a Steam developer key.
Tumblr OAuth 1 http://www.tumblr.com/oauth/apps
TwitchTV OAuth 2 http://www.twitch.tv/settings?section=applications
Twitter OAuth 1 https://dev.twitter.com/apps
Vkontakte OAuth 2 http://vk.com/developers.php
WordPress OAuth 2 https://developer.wordpress.com/apps/
YahooOpenID OpenID