Two places I find great patterns are on LionBrand.com and Ravelry.com. You have to register with the sites in order to access the patterns, but it's free
Another place I've found some neat novelty blankets/afghans is KnittingOnTheNet.com (no sign-up and the patterns are free).
I've made the Plush Throw from the Lion Brand website, and actually modified the dimensions to make it bigger - it's a simple knit, but the recipient loves it!
I don't seem to make many adult-sized items these days - lots of people at work with lots of babies! I just finished my first raglan sleeve pullover for a 6-month-old, and it's cute as all get-out, if I do say so myself!
Good luck in your search!