You may know some of the below already, but it took me a long time to fish through craftster and various other websites to find this info. It's valuable to me, so I'm posting just in case.
*I used an ordinary pair of scissors
*Only "real" CDs work for this project--CDs that you use to burn music on don't work (so you can't use old burned CDs)
*I didn't want to waste money on a styrofoam ball--yeah, I'm cheap--so I used a scrunched up piece of old (but clean) aluminum foil instead. I've never had experience with glueing CD pieces onto styrofoam, but I really liked the foil ball because the glue (I used hot glue) seeped into the cracks and made the CD piece stick better. http://www.boomspeed.com/clementiney/yaybulletinboard.jpg
This isn't that great, but as I was photographing the disco ball I suddenly wanted to post this as well. It's a bulletin board made from an old picture frame that my mom was going to throw out. I stuck two pieces of corrugated cardboad in the place where the picture should go after covering it with white wallpaper. It works just as well as a cork bulletin board.