Freckle - http://letsfreckle.com/ - made by a very small team, very usability oriented. Came into a tough space, and is now making a ton of money.
This is not me being all "I DID ALL THE WORK WOOHOO!" -- far from it. I'd just like to note that there is far more that needs to be done for a successful app than just code + design. I think people don't realize that, when they see 1 or 2 creators listed by narrow roles, for a successful product.