Plist Pad is a Propertly List / Plist file editor for Windows (and soon, OSX and Linux). It is intended to bring a friendly and simple to use interface to Plist editing on operating systems other than OSX and will provide a number of features in the future to make editing large plist files easier (such as find/replace).
Today you can download a preliminary build of Plist Pad for testing purposes. While it should be pretty stable, it only works for XML based plist files at this point in time.