When you say 'ungroup' I presume you mean separate them out of their grouped folders.
There are two ways to deal with this. You can do it on the iPhone itself or you can do it from within iTunes.
To do this from within iTunes:
Plug the iPhone into your PC or Mac using the supplied dock connector cable.
Select the iPhone in the sidebar on the left. Select the Apps tab in the main part of the window. You will see a list of your installed apps and a representation of what your iPhone's screens look like.
Double click on the group folders. Now you can click and drag the app icons out of the folders. You can even drag any app icon in any order that you want to customize the arrangement.
When you're done click on the sync button to send these changes to your iPhone.
To do this on your iPhone:
Hold your finger down on any app icon until they all start to wiggle. At this point you can hold your finger down on the icons and drag them around the screen to re-arrange them.
For the ones in folders, tap on the folder. you can now drag those icons out of the folders on to the main screen. Once you've dragged them all out of folders you can continue to drag them around in any order you choose.
Once you are satisfied with their placement, hit the home button to stop the wiggle. Your now ready to continue to use your iPhone.
