Check out this video Demonstration of how to add social bookmarking buttons like Digg, SumbleUpon, and del.icio.us to the bottom of WordPress.com blog posts.
A quick tutorial on using GetSocial to add social bookmarking buttons to your WordPress.com blog posts. It actually works with any blog, but it was specifically designed for WordPress.com users who currently have no way of adding social bookmarking buttons to their blogs. If you like this video, please check out my blog: earthshattering.wordpress.com