goldenapples

This plugin aims to support community link-sharing, social bookmarking, and discussion of links in the WordPress environment.
This is still at an early stage of what I hope will be a much more ambitious project. If you want to try this out, please give me feedback.
I will guarantee backwards compatibility with all data saved by the plugin, so it should be safe to install and activate, and as I add features, your existing posts and links will work with them just fine.
See the plugin’s <a href="https://github.com/goldenapples/recommended-links/wiki" rel="nofollow ugc">wiki page on github</a> for more up-to-date documentation (its hard to keep documentation updated in multiple places).

Scott Grayban

It puts a bar of icons at the bottom of each post allowing your readers to submit your posts to several different 
social networking and bookmarking sites. (del.icio.us, digg, fark, etc.)
The original plugin was called <a href="http://blog.calevans.com/2006/02/08/notable-another-wordpress-plugin/" rel="nofollow ugc">wp-notable</a> 
but no longer worked or was supported. The author was Cal Evans.

notable

Adds social bookmark links to each blog entry.

Recommended Links for WordPress vs notable