I made these for a shower gift. They were super simple. The zipper at the top of each is the only slightly tricky part. One is full size and can hold 20 diapers or so until you can wash them. The smaller one can hold 3-5 and can be used in your diaper bag while you are out.
Also, one of my friends pointed out that you can use this for wet bathing suits or other damp items you wish to take home that you would normally throw in a plastic grocery bag. I might have to make another one for Martin when I start potty training him.