The activity is featured on a website called Read, Write, Think.
Venn diagrams are a great way for students to compare and contrast all manner of things, from characters in a narrative to number and science facts.
This online Venn diagram seems simple enough to use and even stage 1 students should be able to follow instructions on how to use it.
I hope you find this site a useful tool. I like that the finished Venn diagrams can then be printed out also, so they could then be put into a student's book. It would also be good for making displays and for presenting information on an electronic whiteboard.