Ask HN: What communication tools work well for Startup Weekend?

With only 54 hours to build an app that's the basis for a business, a bunch of people who haven't worked together before will be doing a lot of things at once. Communications challenges minimizing internal misunderstandings, include getting feedback from potential users, avoiding unnecessary chaos, planning for success by recording as much useful information as possible in case the business goes forward.<p>What tools (chat, wikis, discussion forums, Google Docs, LiquidPlanner, ManyMoon, Basecamp, StackExchange, etc.) -- work well in this situation?