I wanna recommend Pandora's Box. It helps you search for apps in the apps store that have promotions going on i.e. Price drops and apps that have gone FREE. Sure, some of the apps are crappy, and I guess that's why they drop the price in the first place. But there are some great apps out there that had a price drop or went free for a limited time. e.g. Peggle had a price drop for awhile few weeks back.