Again there are a few extensions to do this but this one looks good (haven't tried it yet!)
from http://www.fortysomething.ca/mt/etc/
Quote
The Shareaholic extension for Firefox makes it easy for you to submit the web page you're viewing to digg, del.icio.us, facebook, google bookmarks, reddit and stumbleupon. If you prefer, you can also e-mail the web page to a friend.
Bonus feature: Real-time statistics from digg and del.icio.us
Check whether the web page you're on has been dugg, and how many times it has been saved on del.icio.us. Stats displayed in your browser, at your request.
from http://www.fortysomething.ca/mt/etc/