Description from Knitty.com:
These hats were made using leftover balls of acrylic yarn in my stash. Any worsted weight acrylic yarn will work great. If you're using leftovers for a two-color hat, you will need approximately 150 yds/135m (single strand) of each color.
German translation of pattern: http://www.landlust.de/index.php?option=com_docman&task=doc_download&gid=21&Itemid=51