I hacked my first gen Apple TV to allow AirPlay.
There are ways to make your Mac, Windows PC, and other devices an AirPlay receiver.
The problem is that only the Apple TV 2 can natively act as an AirPlay VIDEO receiver. Most apps which rely on the native iOS video player can take advantage of AirPlay (iOS 4.3 required for apps besides YouTube and Videos, those latter two only require 4.2.1).
