Recently Haiku Deck launched an invite-only web app version of its powerful presentation-creation app. It allows users to build presentations online and then pull them up on their iPads for updating/presenting at a later date. The initial trial period has been a success, so the company is opening up the web app to all users.
Simply head over to http://www.haikudeck.com/ and get started. When you're done with your project, it can be exported to the iPad app, to a PDF or to a PowerPoint file. For frequent power users of Haiku Deck, the ability to keep working on your project -- even when your iPad has run out of juice -- will be a nice addition to your weekly productivity.