A neat little pattern from Cabin Fever, designed by Lynda Gemmell.
The pattern uses a "trick' of a raised decrease on four sides continuing up to the top of the hat. The ribbed band is knit on small needles for a good fit and the upper part of the hat is knit on larger needles.
You will want to use three colors of sport weight yarn with about 110 meters/120 yards per 50 gram ball. You can also knit this hat with double knitting weight yarn but the hat would likely end up a bit bigger.