Perfect Video lets you put your video together with video & photo clips, text, transitions and music. When you are finished, share the completed video to your camera role. (You don't have to use this program if you don't want to add anything to the video.)
What about collaboration on the iPad? Well, a number of the tools in this listing will work fine on many platforms, but Titanpad is geared specifically towards the iPad. TitanPad lets people work on one document simultaneously, and you can get a space for your team on your own private subdomain for free.