On the WhyJoomla.com site today Qasim Virjee has a quick tutorial showing how to add in a module to your Joomla site that talks to the Tweetmeme website with just a small bit of code.
When you take a peek at the tweetmeme page containing the necessary embed code it may not be too easy to tell how to use it with your Joomla site - and though there's a couple of plugins/extension floating around Joomla, it may not offer the flexibility you require for clean theming/templating. However, there's an easy way to go about embedding this and all it takes is a small modification of the de facto embed code.
It really just boils down to about five lines of Javascript that can be customized to pull just the information you want (like article templates or article lists). Then it's just a simple matter of dropping it into your template and adding it to the site.