Example of buttons

btn-adn
<a class="btn btn-block btn-social btn-adn">
    <span class="fa fa-adn"></span> Sing in with App.net
</a>
btn-bitbucket
<a class="btn btn-block btn-social btn-bitbucket">
    <span class="fa fa-bitbucket"></span> ... Bitbucket
</a>
btn-dropbox
<a class="btn btn-block btn-social btn-dropbox">
    <span class="fa fa-dropbox"></span> ... Dropbox
</a>
btn-facebook
<a class="btn btn-block btn-social btn-facebook">
    <span class="fa fa-facebook"></span> ... Facebook
</a>
btn-flickr
<a class="btn btn-block btn-social btn-flickr">
    <span class="fa fa-flickr"></span> ... Flickr
</a>
btn-foursquare
<a class="btn btn-block btn-social btn-foursquare">
    <span class="fa fa-foursquare"></span> ... Foursquare
</a>
btn-github
<a class="btn btn-block btn-social btn-github">
    <span class="fa fa-github"></span> ... Github
</a>
btn-google
<a class="btn btn-block btn-social btn-google">
    <span class="fa fa-google"></span> ... Google
</a>
btn-instagram
<a class="btn btn-block btn-social btn-instagram">
    <span class="fa fa-instagram"></span> ... Instagram
</a>
btn-linkedin
<a class="btn btn-block btn-social btn-linkedin">
    <span class="fa fa-linkedin"></span> ... LinkedIn
</a>
btn-microsoft
<a class="btn btn-block btn-social btn-microsoft">
    <span class="fa fa-microsoft"></span> ... Microsoft
</a>
btn-odnoklassniki
<a class="btn btn-block btn-social btn-odnoklassniki">
    <span class="fa fa-odnoklassniki"></span> ... Odnoklassniki
</a>
btn-openid
<a class="btn btn-block btn-social btn-openid">
    <span class="fa fa-openid"></span> ... OpenID
</a>
btn-pinterest
<a class="btn btn-block btn-social btn-pinterest">
    <span class="fa fa-pinterest"></span> ... Pinterest
</a> 
btn-reddit
<a class="btn btn-block btn-social btn-reddit">
    <span class="fa fa-reddit"></span> ... Reddit
</a>
btn-soundcloud
<a class="btn btn-block btn-social btn-soundcloud">
    <span class="fa fa-soundcloud"></span> ... Soundcloud
</a>
btn-tumblr
<a class="btn btn-block btn-social btn-tumblr">
    <span class="fa fa-tumblr"></span> ... Tumblr
</a>
btn-twitter
<a class="btn btn-block btn-social btn-twitter">
    <span class="fa fa-twitter"></span> ... Twitter
</a>
btn-vimeo
<a class="btn btn-block btn-social btn-vimeo">
    <span class="fa fa-vimeo"></span> ... Vimeo
</a>
btn-vk
<a class="btn btn-block btn-social btn-vk">
    <span class="fa fa-vk"></span> ... VK
</a>
btn-yahoo
<a class="btn btn-block btn-social btn-yahoo">
    <span class="fa fa-yahoo"></span> ... Yahoo!
</a>

Variations of sizes

<a class="btn btn-block btn-social btn-facebook btn-lg">
    <span class="fa fa-facebook"></span> Sing in with Facebook
</a>
<a class="btn btn-block btn-social btn-facebook">
    <span class="fa fa-facebook"></span> Sing in with Facebook
</a> 
<a class="btn btn-block btn-social btn-facebook btn-sm">
    <span class="fa fa-facebook"></span> Sing in with Facebook
</a>
<a class="btn btn-block btn-social btn-facebook btn-xs">
    <span class="fa fa-facebook"></span> Sing in with Facebook
</a>
<a class="btn btn-social-icon btn-lg btn-facebook">
    <span class="fa fa-facebook"></span>
</a>
<a class="btn btn-social-icon btn-facebook">
    <span class="fa fa-facebook"></span>
</a>
<a class="btn btn-social-icon btn-sm btn-facebook">
    <span class="fa fa-facebook"></span>
</a>
<a class="btn btn-social-icon btn-xs btn-facebook">
    <span class="fa fa-facebook"></span>
</a>

How to use

1. Include Bootstrap and Font Awesome to your project

<link href="/path/to/css/bootstrap.min.css" rel="stylesheet">
<link href="/path/to/css/font-awesome.css" rel="stylesheet">

2. Include the CSS bootstrap-social.css

<link rel="stylesheet" type="text/css" href="/path/to/css/bootstrap-social.css" />

3. Add buttons:

<a class="btn btn-block btn-social btn-facebook">
    <span class="fa fa-facebook"></span> Sing in with Facebook
</a>

or icons:

<a class="btn btn-social-icon btn-facebook">
    <span class="fa fa-facebook"></span>
</a>

Link to site of plugin: http://lipis.github.io/bootstrap-social/