Skrbl is an online IWB with simple writing and drawing features but very interesting collaboration possibilities.
You can type, draw or write freehand, and use straight lines and shapes in your drawings.
The most interesting thing about skrbl is the ability to share your work with other people. The paid version ($10 a month) includes video conferencing and all sorts of interesting things. But it would be easy to get started with the free version. How about using it to play a game with another class in the school (such as guess my number, 20 questions (If the teachers also used their mobile, this could be very effective!) Or you might want to collaborate with another class to brainstorm a solution to a problem e.g. “how can we reduce the amount of rubbish in the school?” The Year 2 class could use red ink, while Year 5 use blue to differentiate the ideas.
You could also use the board for collaborating with schools in other parts of the country, or the world! Using MSN or Skype in another window could help co-ordinate turn taking etc. A question like “Describe your town” with categories such as shops, parks, people, favourite things etc. could be very interesting for both classes.

