ImageOptim - Faster web pages and apps.
Image Converter Plus - Image Converter Plus is a multifunctional conversion and resizing tool for Windows operating system.
XnConvert - XnConvert is an easy image converter for graphic files, photos and images available on Windows...
ImBatch - ImBatch is a batch image processor with a nice graphical user interface.
JPEGmini - JPEGmini - The Photo Optimization Tool Trusted by Tens of Thousands Image Perfectionists
FileStar - With FileStar you can "do anything with any file".