wow – I had never heard of this before, but what a lovely thing: http://www.altmetric.com/bookmarklet.php
A link in your bookmarks that will tell you if the article you’re interested in has been tweeted, blogged about, added to Mendeley etc. A way of getting a feel for the impact that an article is having.
Using this for particularly new articles, that haven’t got any citations yet could be really interesting.
Easy to install (firefox, chrome or safari only at the moment) it looks like a tool I could easily become quite addicted to!