I have previously mentioned BeFunky on this blog (9/21/2010 and 01/31/2011) As stated on their blog: BeFunky simplifies photo editing and effects for everyday people.
Check out how this classroom teacher in England used this web 2.0 application in his classroom, BeFunky In Your Classroom.
I checked their Terms/Privacy section again today and it states that users need to be 13 years of age so I am curious as to how he was able to use it with 8 and 9 year old students. But the app is certainly easy enough for them to use and there is no registration requirement where any information about them could be stored. To begin they just need to click the Get Started button. Then they have the option of clicking on six boxes: Edit your photo, Apply Photo Effects, Apply Artsy Effects, Add Graphics, Shapes, add Text, Speech Bubbles or Add Frames, Borders. After selecting one of these boxes a photo needs to be uploaded.
With parental permission for a classroom activity this would certainly be possible.