Have you seen Padlet (was WallWisher)? It's on online 'wall' where sticky notes can be added. It allows anyone with the link to the page to add to the content of the wall.
Here are three examples of its use:
My newest idea for using Padlet is as a replacement to sugar paper. How often do children in your class work collaboratively while huddled around a piece of sugar paper passing a marker pen between them to add content? How about providing them a Padlet wall to write on? Either one for the whole class, or one per group. Start with a blank wall or possibly start with a prompt in the middle (a photograph for example). Then at the end, the class teacher can project the results or get each child in turn to visit the other walls to see what's been written. Also, there's no need to store rolls of paper for future reference. Just keep the links!
The walls above are on going throughout the year and therefore all posts are moderated. If I was using a wall within one lesson I'd probably leave it unmoderated so results were put live instantly.
If you have other uses for Padlet please let us know.