Most of you already know that you can make and utilize folders pretty easily with Ice Cream Sandwich, Basically, from one of your home screens, you tap and hold on any app icon and move it over another app, release it, and walla, you have a new folder. To add apps to that folder or any other existing folder, you just tap and hold any other app icon and move it to the already created folder and release it.
What you may not know is that you can do this within the launcher tray as well. With Ice Cream Sandwich, you are given 4 spots for any apps you choose. Assuming you already have an app in one of the 4 spots, just tap and hold on any icon that is on your home screen and move it right over the existing app in that spot, release it, and you will create a folder. Of course, you can add more apps just like any other folder. Why would you do this? It allows you to free up even more space for your gorgeous wall papers or if you want to have larger widgets on your home screens. It also gives you access to those folders on every home screen which is very convenient. I did up a short video showing you how it works.