iPhone apps I actually use

It would be cool if there were an app that told you what apps you use. Of the 4 screens of apps on my phone, the ones that get used the most are the built-ins (iTunes, iPod, calendar, mail, safari, maps), and those relating to news and weather (AP Mobile, NYTimes, WeatherBug) and, of course, Facebook. Now I’m pondering whether I should reorder the apps so the most frequently used are on one screen. (There’s another app that would be useful, one to reorder apps by name or by frequency of use or by recency of use.)