Muito simples de integrar. Usei um destes para OpenCart.
Social Button Collection
Includes differnt shapes and sizes of attraive social media buttons in css which can be easily added to your existing website code.
Pure Social Buttons in css3
A rolling effect with horizontal display of modern social icons will blow your mind.
Fancy Buttons
Another visual treat to the website visitors to share your content or bookmark the website on their timeline.
Hover Fancy
This time you will find a different hover style which ends with a text display.
Sexy Social Buttons
Color effect on hover will display the original color of the top social network websites.
Social Buttons Slide
Four major social media networks which can be showed up in your blog with vertical slide animation. The snippet also shows the social counter stats of your page or shared link.
Social Footer
Social Footer with long shadows which can be used on footer of the page.
Social Section
A set of social icons with nice hover effect.
Social Share
A social sharing icon set with three popular networks Google, Facebook, Twitter.
Social Networks
A bar of fixed social networks.
Circular Social Icons
A three icons showcasing Google, Facebook, twitter in all its glory.
Share Buttons
A set of social media share buttons with a 3D effect that makes you want to click them!
Color Changing Social Bar
On hover on any of the social network icons the background portion will change color similar to the network.
Flat Social Buttons in CSS3
A long version of share buttons to match your website sidebar.
CSS Social Ribbons
Simple yet stylish CSS Social Ribbons.
Social Navigation
A vertical style navigation.
Fonte: 15 Free HTML CSS3 Social Media Buttons
Hom Digitalis 