Since this was recently posted on lifehacker, I just thought of highlighting this script for people who don't use GreaseFire or monitor the recent Greasemonkeys:
Gmail Unreads Summary
Author's Page:
http://www.winstonyw.com/2009/08/08/greasemonkey-script-gmail-unreads-summary/
...It doesn't empty the inbox or help you unsubscribe newsletters but I find that I prefer it this way then having an empty inbox or worrying about which newsletter to unsubscribe.
Gmail Unreads Summary
Author's Page:
http://www.winstonyw.com/2009/08/08/greasemonkey-script-gmail-unreads-summary/
...It doesn't empty the inbox or help you unsubscribe newsletters but I find that I prefer it this way then having an empty inbox or worrying about which newsletter to unsubscribe.