Share-lanyrd-event-chrome is a project mainly written in JavaScript, it's free.
Add links to the Lanyrd website in Chrome to share events on Facebook and Twitter
This extension adds links to events on the Lanyrd social events website to share events on Facebook and Twitter. This is an example of just how easy it is to create Chrome extensions to modify pages on-the-fly with jQuery.
Say what? I don't care about the source!
If you don't want the source, and just want the nice little extension, download it on Google Chrome Extensions.