Chrome: Google just launched its new Google+ Hangout extensions in beta, including its drawing app, Sketchpad, but Conceptboard takes it a considerable step further and adds full whiteboarding support.
The extension sits invisible in Chrome until you start a hangout in Google+, after which you'll be able to hit the Conceptboard button to start collaborating with others. We rather liked the web app and iPad versions of Conceptboard, and the Google+ integration makes it easier to work with friends and coworkers.
Better still, you don't need a Google+ account to join and work on the board. When you're finished, your work will be saved over on Conceptboard's main site. It's still in beta, but it's a free download and didn't pose any major issues for us.