To promote legitimate apps in the forums and to sway people from using cracked apps, I will post here apps that are on sale for a given period. There are alot of $0.99 (even free) games and apps that is otherwise regularly priced at $5, $6, $7 and more.
Some great free apps that I highly recommend are:
AppShopper

AppShopper is a very good app that catalogs the apps found in the AppStore. It can show price changes so you will know which app had went on sale or became free. Some apps that are for sale sometimes go free for a day due to some promo and such and with AppShopper you can be sure to be in the know. The best feature of AppShopper is the wishlist feature. For registered users, you can search for the app or game you like and add it to your wishlist. If the app had a price change, update, or sale you will be notified by AppShopper.
FreeAppADay

This app used to be free but they started to charge now. With this app you will receive free notification of apps that went free for that day only. Although most of the free apps they give out is crap, it sometimes bring out free apps that are true gems (Mobile Air Mouse, Super KO boxing and more).
Transfer your purchases

Once you have downloaded your apps, be sure to transfer them to your iTunes library so you can have a local copy. Even if the free apps go back on sale at their regular price, you can still re-download it from the AppStore or iTunes since you have "purchased" it for free before.
I encourage everyone to post whatever app or game they find that are free or on sale in the following format:
1. App Name
2. Photo or screenshot
3. Price before and after
4. Date valid
Hope this will help a lot of people here who want to stay or go legit in a budget conscious way.