Today, November 11th, is World Usability Day. To celebrate, the good folks at Clearleft wil be donating all revenue from sales of Silverback, their Mac ‘guerilla usability testing’ app, to the Dian Fossey Gorilla Fund.

Silverback’s a great app [full disclosure: I did some work on the latest version, but I’m pretty sure I would think this regardless] for performing quick, simple usability testing of your Mac app, web app or web site (or even Windows app with VMWare or Parallels!). It records what’s happening on screen, along with the user’s reactions using the iSight camera, and you can play…