Apps with 'Alpha Channel' feature

  1. Paint.net is a free and very capable image editing software for Windows. Great alternative to Photoshop for people that do not need all the stuff PS offers.
  2. ImageAlpha is a GUI for pngnq and pngquant. It allows you to easily generate paletted PNG images with full alpha channel. These images are usually 40-60% smaller than 24-bit PNG, and still can have semitransparent colors.