37Signals' Chalk, iPad-only collaborative web app

37Signals is well-known as the developer of some powerful collaboration tools for the Web like Campfire and Basecamp. It's obvious that the employees of the company know how to use a chalkboard to sketch out flow charts, scrawl UI mockups, and so on.

In fact, the four team rooms in the company's new offices have corkboard walls and large chalkboards to facilitate brainstorming, and 37Signals employees wondered if they could take those chalkboards with them everywhere. The result? Chalk, a free iPad-only web app.

To use the free Web app, just use Safari to point to chalk.37signals.com, and then tap the plus sign in the Safari toolbar to add the site to your home screen. Don't worry -- you needn't be on the Internet to use the app. Once you've created the home screen icon, the app persists and will load whether or not you're connected.

Chalk is simple: you have a piece of pink chalk, a piece of white chalk, and an eraser. There's a chalkboard, and for some reason, there's a light switch on the wall. I think it's there just for fun and realism. To save a drawing, just tap the share button, then tap and hold to either save the image to the Photo Library or to copy it.

To learn more about Chalk, check out the video on the next page.