I often use Paint .NET to make or modify sprite sheets, and one of the things I've always wanted to do was see the animation in action without having to leave Paint .NET. This plugin will allow you to do just that. It lets you view any sequence of animations within a sprite sheet by adjusting the offset, # of columns, and the total # of frames. You can also save all the frames off to individual .png files. Saving an animation as an animated GIF is also supported. New version available (