Twiddla means collaboration
Twiddla is a "web-based meeting playground." It allows you to use the great features of Titanpad, and more! Mark up websites, graphics, and photos, or start brainstorming on a blank canvas. "Browser-agnostic, and user-friendly." Create a Twiddla session, invite users and begin. You can save the results of your collaboration to revisit another time. (Unfortunately, like the other Etherpad-based sites, it doesn't work with the iPad.)
