I give them a large notecard for each planet to take notes on. They use these notes to generate the facts on each card of the stack. The pictures come from various videodiscs and videos that we use as well as the internet. We also scan some pictures from books. Since these are interactive, I usually hold a sharing day in the computer lab.
Students can then move around and investigate each stack.
Fortunately, my school has a network server with lots of storage. This allows me to create files of pictures for my students to insert into their stacks. They save their work on special folders on the server so that they can access their stack from any computer in the school. If you have limited storage, you might want to make a class stack where groups of students create one card each. My students have used Hyperstudio a time or two before this project, but I find that if you teach them a skill or two at a time and give them a chance to practice it, they master the software quite easily.