1) AppAdvice.com Apps Gone Free :
AppAdvice is one of the best App review sites out there. They have an Apps gone free section which can be accessed via the web or via an app which highlights the best apps that have gone free. Only the best hand picked selection make it to this section so rest assured this site is worth your time. I have discovered some pure gems on this site and visit it on a daily basis.
AppShopper is probably the best app tracker out there their site provides a list of top paid/ top free/ top grossing apps out there for Mac / iPad / iPhone and iPod Touch. They even list all the newly listed apps out there and provide reviews on major releases. Do check them out.
3) FAAD, DailyAppDream, Apple's Free App Of The Week, Apps-aholic etc.
Ok there are tons of sites like these. I usually don't check them out because the 1st two of my recommendations usually cover them. The advantage these sites have over the first two is they don't just limit themselves to the Apple / iOS environment. Most of these sites offer daily email updates which might come in handy if you want an app fix. The list:
So whats your favorite site ? Leave your suggestion in the comments below.