About ten years ago, I randomly thought it would be nice to make quick CD sleeves for all those random burned CDs when there aren't any around. I toyed around a bit and came up with this. Nearly everyone who has seen me doing it has used it now and again and often more again and again since, and eventually I put up a brief page on it but I think this is the place people ought to see this sort of thing.
Step 1: Material
Start with a piece of paper, letter or A4 is good. It doesn't have to be unused, any scrap paper given/sent/pre-used works fine.
Step 2: Start Folding
Fold the bottom half up far enough to render the whole thing about 5 1/4 inch high. This usually means around two inches gap (more won't really be as much of a problem as less - around 5.6 cm (2 1/5 inch) on an A4. Ain't unit conversion grand..) between the top and folded up part..
Step 3: Keep It Up
Flip it over, the folded side now facing down. Fold one end over toward the center. There is plenty of leeway here but not too far from the edge, leave plenty of room and aim for around half or so.
Step 4: Other Side
Fold the other side over toward the middle, leaving about (again) 5 1/4" total. On a US letter paper, you will be overlapping around 1/4 inch between them. Eventually it'll be second nature. Around the size of a CD, no biggie. 1.5 cm (2/3 inch) on an A4.
Step 5: Tuck
Tuck one of the flaps inside the other. This will keep the thing together.
Step 6: Insert CD
Flip over and tuck CD slated for storage into it. It isn't hanging in the air like a jewel case, but certainly much more safe from scratch and fingerprint than before.
Step 7: All Done
You have produced a reasonable storage for data. They go very well in 5 1/4" disc boxes or even normal cd storage things that expect the DJ style sleeves. A leftover shoe box can also keep 100 (i.e. ~70Gb) of these.