If you like Font Awesome, you're going to love Black Tie!
             

fa-stumbleupon-circle · Unicode: f1a3 · Created: v4.1 · Categories: Brand Icons

After you get up and running, you can place Font Awesome icons just about anywhere with the <i> tag:

fa-stumbleupon-circle
<i class="fa fa-stumbleupon-circle"></i> fa-stumbleupon-circle

Looking for more? Check out the examples.