Three apps for stacking images for noise reduction or long exposure effects.
Starry Landscape Stacker for night landscapes with stars as points.
Starry Sky Stacker for images of the sky taken with the camera on an equatorial mount.
Long Exposure Stacker for noise reduction or long exposure effects in images taken during the day. Also useful for making low-noise images without a tripod (for example, in places where tripods are not allowed).