There are quite a few sites with the basic project as in the link. The problem with that project is that you either print the PDF (and usually have spare cases empty) or you "follow your feel" with widths and sizes, resulting in the case too big, too small, or otherwise wrong.http://www.google.pl/search?q=origami+cd+casehttp://www.papercdcase.com/Any better CD case.envelope projects? Especially ones that contain some methods of creating creases at specific distances to get the size right without a ruler.
Will this help ?
if you can't get the lengths right, why not try putting a cd on the paper while folding it? then it'd be all but impossible to fold it the wrong width and height.