Here are free instructions: http://www.girlythingsbows.com/wipe_cover.html
Ballerinasandbucaroos has a great paid tutorial. I got mine from her a few years back, and put my own spin on it. She's here and etsy.
\I like how huggies looks, but my personal ones are pampers.
Here are a few basic ones I've made: http://sweet-baby-michele.webs.com/diaperwipecases.htm