I was trying to explain this to someone the other day and decided it would be easier (and fun) just to make one to post. This is a CD case invitation--I got the idea a few years ago from http://www.thestampingstudio.com/. I have done these for a couple of my kids' birthdays, and they're a bit of work but they're so cute! I thought the Just 4 You Simply Scrappin' Kit would make adorable baby shower invitations, so that's what I tried this time.
It is made using a standard size cd jewel case. I just buy mine at Target or Walmart. The hub has to be snapped out of the case (gently!). I decorated mine mostly with the stickers that came in the SS Kit. I also used the "Happy New Baby" stamp from the For a Friend set and colored it in with blender pens. I popped some of them up on dimensionals. A couple of them (the white circle with the green flower and the green circle with the butterfly) a mounted on paper and cut them out so they wouldn't be sticky. That way they float around in the box as you move it. I also added some mini diaper pins that I got a long time ago at a scrapbook store (so I couldn't tell you the brand name).
The most complicated part to explain is how to close the case up because it will have a hole down the side near the hinge (from removing the piece of plastic with the hub on it). I solved this problem by folding a small square tube of thin cardboard (I used the cardboard that comes in the back of SU's paper packs). I secured this inside the case to close up the hole. I then closed the case up and secured the edges with some clear tape. Next I added another piece of DSP along the "spine" of the case to hide the ugly stuff and tied a piece of ribbon around it. Ta-da!