AirView is a free app that turns iPhone, iPod Touch or iPad into an airPlay receiver to stream video on other iOS devices. It is also possible to stream content from a PC or Mac running iTunes, meaning that you can view videos of almost any length without having to worry about file size.
The idea is a simple one, and the only real requirement is that all of the devices involved need to be on the same wireless network so this unfortunately means that the app cannot be used to access your media files while out of the house.
[advt]There are a few issues with occasional sound problems and the fact that DRM content can only be streamed to Apple TV rather than any AirPlay device, but it is still early days for AirView. The app shows signs of promise and while it is worth taking a look at right now, there are undoubtedly better things to come in the future.
Fire up your AirPlay app on the device you want to watch on, and load a video on another device, like iTunes. In the video window, you should see an AirPlay icon click it, and the program automatically detects your receiving device and streams the video over a local Wi-Fi network to the other device. AirPlay seems to work best for YouTube and downloaded videos.