Caesium Image Compressor - Compress your pictures up to 90% without visible quality loss.
Online Image Converter - Online Image Converter converts your BMP, JPG, PNG, GIF or ICO files quickly and easily.
FastStone Photo Resizer - Convert and Rename images in batch mode Support JPEG, BMP, GIF, PNG, TIFF and JPEG2000
Faviconer - Faviconer.com, or favicon generator, is online tool for creating favicon.
ImageMagick - ImageMagick is a software suite to create, edit, and compose bitmap images.
Ordinatore - Those who want to tidy up their Macs will surely love this application.