Collective.addthis is a simple Plone addon which brings addthis.com services to Plone CMS.
Collective.addthis has customizable addthis url (pointing to your AddThis username) and AddThis javascript url (pointing to addthis javascript url). By default those settings have random values I got from addthis.com so that testing collective.addthis would be easy. Those values are recommended to be changed if you're planning to use this addon in production.
There are few other similar addons for Plone which does the same job with different approach. If collective.addthis doesn't do the job for you I suggest to check these out too: