Got a baggy hat that's otherwise cute? Try running a piece of elastic cord through it at or near the brim. Louise, my learning-to-knit-neighbor, knit this cute hat from Homespun but its circumferance got out of hand. One of the other ladies in our knitting class mentioned the concept for charity hats that would fit multiple head sizes.
Since the hat is done in stockinette, the brim rolls up over the elastic, and the hat looks good on everyone who's tried it so far (no guys have tried it, though).