iTunes link: HotDealsApp
The premise behind Hotdealsapp is pretty straightforward. It simply lists applications that have been reduced in price or have been changed from paid apps into free apps. You can view the app deals either by popularity or by the most recently reduced and there’s also a section that lists only free apps. Clicking on an app in the list reveals its full details along with a link to the app store, where you can make your purchase.
Naturally you can also search the database of apps to find specific ones you’re after. You can even sign up for a free account and mark apps you’re interested in. The software will then let you know the next time they go on sale via a push notification.