Tagxedo. I know I have written about this one before but I think that many still don't know about this one.
With this cloud you can have the words shaped (for example I have used an angel) and also you can save it as a jpg file onto your hard drive which is not possible with other word clouds. All of this is free. You can customise the colour, the theme and the shape to suit what you are doing. I know that children will love using this one.
Hardy Leung has done a presentation to show you how to use Tagxedo in 101 ways! Each way gives you an illustration to show an example. Very useful for classroom teachers for ideas to use in their classrooms.