I just added ShareThis to Colorbox. Here is my code.
Add this to your jquery.colorbox.js (uncompresses / unminified) file around line 360 inside the publicMethod.init function immediately after defining the $ wrap object.
// Add shareThis
$wrap.append(
$div("ShareThis").append("<span class='st_facebook_large' ></span><span class='st_linkedin_large' ></span><span class='st_twitter_large' ></span><span class='st_stumbleupon_large' ></span><span class='st_gbuzz_large' ></span><span class='st_sharethis_large' ></span><span class='st_email_large' ></span>")
);
Add this code to colorbox.css to align the vertical ShareThis panel on the left side of the browser when the modal format is displayed.
#cboxShareThis {
background: #fff;
padding-top: 25px;
position: fixed;
left: 0;
top: 25px;
width: 40px;
z-index: 9999; }
ShareThis sharethis.com, , colorbox.
<script type="text/javascript">var switchTo5x=true;</script>
<script type="text/javascript" src="http://w.sharethis.com/button/buttons.js"></script>
<script type="text/javascript">stLight.options({publisher:'YOUR_UUID_GOES_HERE'});</script>