Appcuity is an application that can help you find new apps. It can search the Mac App Store to find applications that have been recently discounted. This includes both apps with reduced prices and those which became free, either temporarily or permanently. The main screen shows the list of apps, which you can filter in many ways. The list shows the name of the applications, their current version, release date, discounted price, regular price, savings, discount percentage, and when the price has been changed. It also shows the Mac App Store rating. You can search for applications using the search text field, or you can click on the "Searches" button at the top and start a preconfigured search. Some of the available ones let you search for free apps, five star apps, recently changed prices, etc.
There is one thing that I like a lot about this app: when you double-click on any entry of the list, a new window pops up and it displays a lot of information about the app in question: screenshots, and links to both the Mac App Store and the developer's website, when available. What I don't like about the app is that it seems slow at times, and the list is too full of information, and since it is all text, it can be hard to find what you are looking for. But once you get used to the way the information is presented, you won't find this confusing any more.