Lately I've been seeing moms with very chic and functional diaper bags - they're made by Petunia Pickle Bottom.
Petunia Pickle Bottom :: Baby Chic. They're made with beautiful fabric and some also can convert to hand carry, backpack or attach to the stroller (awesome feature!!). I wish I still had a need for such a cute diaper bag because I'd get one in a heartbeat.
Also, I've found that when I'm on a long trip or day trip somewhere my Baby Innovations Backpack Diaper Bag - which has a separate cooler and separate diaper storage - was indispensible. Plus my husband was fine carrying it. Backpack's great when you have two little ones and need to free up your hands.