Android likes to think of itself as more of a computer-like mobile operating system than some of its competition, and it is on the verge of receiving the one app that any OS needs in order to earn its stripes - a torrent application.
The following tutorial will enable you to move your downloaded Youtube videos on your iPhone to the camera roll app. This will give you complete video editing capabilities of iPhone 3GS with which you can trim and share your downloaded videos on your iPhone, and then sync them with your PC or Mac. You can also make it work with your iPhone 2G, 3G and iPod touch by first following the tutorial posted here on How-to: Enable iPhone 3GS Video Editing and Camera Roll in iPhone 3G, 2G and iPod touch before following the guide posted below.