Those of us who have sold items on eBay know that packing materials can really cut into your profit margin after all the fees (Damn you, PayPal!) and this is especially true when selling CD's which don't net much profit. Using padded envelopes is expensive and wasteful because they are mostly plastic. I always reuse the mailers whenever I get them from things I have bought but it would still be better if we all stopped using them altogether.
Cut the Initial Shape
For this project, you will need scrap cardboard that is a minimum of 10 inches by 13 inches that is preferably unbent. If you don't have an extra box lying around that is big enough or even none at all, you can get some for free at many retail stores or markets. Think of when you last looked for boxes for moving.
Once you have a proper size piece of cardboard, draw a 10" (W) by 13" (H) rectangle and cut it out.
Give it Wings
Next, remove two 2" (W) by 8" (H) rectangles in the bottom corners.
Score!
Lastly, you will need to create the creases so you can turn this into postal origami. I find it helps to mark all the score lines first, and then actually do the scoring.
For the top of the 'T', make the first line 1.25" from the edge on each side and the next one 0.75" from the previous line.
At the "neck" of the 'T', make a line aligned with the bottom of the side flaps and another 0.75" below that.
The final two lines are 1.25" and 0.75" above the bottom edge respectively.
When you are done, it should look like the photo above and it's now time to score (bend) these lines. Use your ruler to push down hard and slightly bend up each flap. It works best on a soft surface like carpet or a bed because these surfaces do some of the actual bending for you. This is what you should now have (although hopefully better looking).
If you are still confused, here is a template. Click it for the full size version.