One of my favorite mitten patterns for years has been Nancy T. McGlynn's Warm Heart Mittens, published in Knitting Now magazine. They're a fun Fair Isle pattern that moves along quickly on size 8 needles (I use size 6 needles for the cuff). The pattern is easily adaptable to color and pattern variations.
During July I made several pair of Warm Heart Mittens, using Brown Sheep Lamb's Pride Bulky Superwash. It was so much fun to play with color. August finds me making hats to match the mittens as I spend way too many hours in front of the TV watching the Olympics.