Keynote

Keynote for iCloud beta is web app that allows you to create and edit presentations using a web browser on a Mac or Windows computer.

You can share a presentation with others by sending them a link to it. Recipients can click the link to view the presentation, and you can also allow them to edit it so you can all work collaboratively. Any changes you or others make to the presentation are saved in iCloud, so everyone always sees the latest version.