Slacker Radio Replaces Pandora when I want general non-stop channels that are customizable
Waze social GPS, maps & traffic Replaces Tom-Tom and any other high cost navigation app. It is really cool to get updates on the road or route you are driving on from others.
AppMiner (Paid Apps FREE) This is my goto app for finding apps (because I hate the app store) and for sorting through all the apps to make a favorites list while I wait for the price to drop.
Replaces AppShopper, FreeAppADay, and OpenFeint (although they are all good apps)
Read It Later Free Replaces Instapaper. I've bashed Instapaper enough, so if you want more, just read my review.
Nebulous Notes Replaces Elements, for all those who do not want to pay $4.99 for a plain text app. This app does anything you would need, it has a lite version and the inexpensive full featured.
Newsy: Video News, Multiple Perspective Replaces almost all news apps for me. Although I still have a full folder of news apps, I always check Newsy first.
Check it out, if you have not seen it yet.
WeatherBug Replaces any other weather app for me. I don't have any real preference, but I find this has the best accuracy and has not crashed on me anywhere near as much as the others.