Facebook: http://www.facebook.com/brandpermissions/logos.php
Github: https://github.com/github/media
Google: https://developers.google.com/identity/branding-guidelines
Launchpad: https://help.launchpad.net/Legal
MyOpenID: https://www.myopenid.com/ [no guidelines available]
OpenID: http://openid.net/add-openid/logos/
Twitter: https://twitter.com/logo