Apps Gone Free is an app for iOS, which is extremely obvious. It highlights apps that have experienced recent price drops. It reminds me of AppShopper, but in this case they get nearly exclusive promotions. Obviously, the apps will be on the app store no matter what app you use to find them, but Apps Gone Free will often create partnership deals. Apps Gone Free works with developers to promote the application, through a ‘bumping’ process which, from what I gather, allows users to vote on apps they want to become free, so that the Apps Gone Free folks can work with other app developers.
It’s very convenient, and you can even scroll through several days worth of items that went free. Several of the deals may have expired and prices gone back up, but you can still what the deals were. And scrolling back is still worth it, because some items may stay at their reduced price for a few days. So go ahead and install Apps Gone Free for your iPhone or iPad and see what deal you can find!