The F in the FIVES Criteria has long since changed from "Free" to "Fairly Priced," but we all love a bargain. One of the best ways to find "finds" is a daily check of the Apps Gone Free app (free). This app, a resource from the terrific App Advice blog and website, lists apps that have "gone" free for a day or so. The apps tend to be of higher quality both because they usually cost some money (not always an indicator of higher quality, admittedly), but also because they need to have a minimum rating of 3 stars in the App Store in order to be listed. Apps Gone Free is a great way to hone your evaluation-at-a-glance skills; take a look at the apps listed and do a quick FIVES analysis (or application of other criteria you find handy) in your mind before you even download. In this case, there's no risk if the app doesn't turn out to be something you could use!
Another feature I like in this app is that you can easily share your bargains with colleagues via email or twitter, so they can grab the app while it is free as well, and perhaps you can collaborate over ideas. Keep in mind to alert them that the apps listed are only free for a very limited time!