In my 8900 phone I'm able to create a folder in the main menu in order to put some of the icons inside.
In the Playbook, as I have now a lot of sideloaded apps, for what I can see, there is no option to create a folder in the main menu and just put some icons inside it.
I really liked to be able to organize the apps in folders.
Hold the icon until it pulses. Drag that icon on top of another. This will create an folder and the ability to name it. You can also drag icons off the side of the screen to create additional panes.