I've been going a little nuts with this pattern I found in the 2007 Crochet Pattern-a-Day calendar at Barnes and Noble (Annie Modesitt & Friends). The pattern is called the "City Girl Cap," and (dated for January 2, 3, and 4) by Celeste Young.
Basically, it's entirely made of front and back post double crochets. The nifty ribbing is little pairs of front-posts running around the crown. These each took me about 2 hours total, each using a little less than a skein. The blue is Lion Brand Wool-Ease Worsted; the green is Paton's worsted Merino (220 yards per skein) and the multi-colored one is made of left-overs of the green and blue plus some left-overs of Cascade 220 in pink from a different project. These are all the same weight and the stripes look great. Here's a close-up:
Here's me wearing the blue one. The striped one is a gift for my cool roommate T.H., but she doesn't know it yet.