Nicolas Gallagher has recently created some nice CSS3 sign-in buttons under public license. The buttons come in 2 different formats (normal, large) and support services like Facebook, GitHub, Google, OpenID, Twitter, Windows Live ID and Yahoo!. The button work great in most modern browsers (Google Chrome, FF 3.5+, Safari 4+, IE 10+, Opera 11.10+). Note that some CSS3 enhancements are not supported in older versions of Opera and IE and use of icons don’t work in IE6 and IE7.
To create the default sign-in buttons you simply need to add a class of btn-auth and btn-[service] to an “a” element ([service] is one of the supported social sign-in services). Check the example bellow.
CSS3 sign-in buttons: Preview