Photopus Pro - Photopus Pro is an easy to use batch image processing to simplify the process to convert, add watermarks (text and image), resize, transform, touch-up, rename, and apply effects to your digital images.
Ralpha Image Resizer - High-speed image batch conversion tool
GraphicConverter - Graphic Converter for Mac and Windows, can converts image formats BMP, JPG, GIF, ICO, PNG, TIF...
ImBatch - ImBatch is a batch image processor with a nice graphical user interface.
BatchPhoto - BatchPhoto is a batch photo editing software for Win and Mac that can convert, resize, annotate and watermark hundreds of photos in one go. Learn more and try it for Free!
Caesium Image Compressor - Compress your pictures up to 90% without visible quality loss.