The Testpad homepage now has a 2-minute video giving a very quick overview of Testpad. Check it out if you're new to Testpad and want a quick way to see what it's all about.
Or send a link to a friend to save you the trouble of explaining it to them!
For the curious: The video was captured and edited on a Mac using the excellent ScreenFlow app from Telestream, and the audio was recorded and processed with the open source tool Audacity. It's hosted on Vimeo for their high-resolution embedded player, as it really needs to be viewed in HD to see what's going on.