Free and open source

GUI tool, to view intensity profile dynamically as the position of ROI is changed by mouse-dragging a ROI. In more recent ImageJ, the native plot-profile window is equipped with "Live" mode, so this plugin function became a part of ImageJ.

This plugin is a good scripting example using Clojure (see source code).

This plugin stabilizes jittery image stacks using the Lucas-Kanade algorithm. It supports both grayscale and color images.

See also this tweet

This plugin generates theoretical PSFs, assuming they arise only from diffraction.