Like an online whiteboard. Invite up to 25 people who can post messages, contribute, highlight, evaluate items on a whiteboard.
You can upload pretty much anything - pdf, image, Word document. Whiteboard has no dimensions and you can upload file after file.
Final design can be downloaded as pdf or image - awesome for planning. Lots of great features I've just found the Presentation mode and hyperlinks for Heading text on the right hand side - HOW IS THIS FREE?????