Adding ShareThis to a Plone Site
Plone's default Document Actions of "Send This" and "Print This" appear as text links in the bottom of the body content.

To add ShareThis, it is necessary to modify the template which controls this viewlet.
Step 1. Create an account at ShareThis and use the Basic wizard to create the javascript embed code.
For this example, I generated the following code:
<script type="text/javascript" src="http://w.sharethis.com/button/sharethis.js#tabs=web%2Cpost%2Cemail&charset=utf-8&style=default&publisher=66a4a04a-cdcf-44ba-9b02-7227f938c209"></script>
Step 2. Through the ZMI, customize <portal>/portal_view_customizations/zope.interface.Interface -- plone.abovecontenttitle.documentactions/
Alternatively, in the file system, look for document_actions.pt. You can create and customize a new viewlet to replace the default functionality.
Step 3. Insert the ShareThis Javascript into the Plone viewlet template
<div class="visualClear"><!-- --></div>
<div i18n:domain="plone"
class="documentActions">
<tal:docactions tal:condition="view/actions">
<h5 class="hiddenStructure" i18n:translate="heading_document_actions">Document Actions</h5>
<ul tal:define="normalizeString nocall: context/@@plone/normalizeString">
<li>
<script type="text/javascript" src="http://w.sharethis.com/button/sharethis.js#tabs=web%2Cpost%2Cemail&charset=utf-8&style=default&publisher=66a4a04a-cdcf-44ba-9b02-7227f938c209"></script>
</li>
<tal:actions repeat="daction view/actions">
<li tal:attributes="id python:'document-action-' + normalizeString(daction['id'])">
<a href=""
tal:attributes="href daction/url;
title daction/description"
tal:content="daction/title">
</a>
</li>
</tal:actions>
</ul>
</tal:docactions>
<div tal:replace="structure provider:plone.documentactions" />
</div>
Step 4. The ShareThis function supersedes the need for Send this so the visibility of the Send this function can be disabled in the <portal>/portal_actions tool.
Examples
Boston.com, Dogtime.com, AccessHollywood.com, SparkPeople.com and FoxBusiness.com
References