If you are planning to put pupils together or have groups peer assessing work you may wish to use the following websites to select a group by number.
There is a dice that can be used. This is similar to the dice function of the Smartboard/Promethean IWB software.
http://www.arcess.com/dice.swf
http://www.schools.bedfordshire.gov.uk/ngfl/IWB/resources/flash%20files/flash/singleDie.swf
For those wanting to use a timer to give pupils a chance to come up with answers there is the timer at http://www.harmonyhollow.net/ct.shtml