FILEminimizer Pictures - FILEminimizer Pictures compresses JPEG photos, TIFF, BMP and PNG images and pictures by up to 98%.
TinyPNG - Make your website faster and save bandwidth. TinyPNG optimizes your PNG images by 50-80% while preserving full transparency!
Caesium Image Compressor - Compress your pictures up to 90% without visible quality loss.
Compressor.io - Optimize and compress your images online. Compressor is a lossy and lossless photo compression tool.
DVDVideoSoft Image Convert and Resize - Free Image Convert and Resize is a compact yet powerful program for batch mode image processing.
Optimizilla - Optimizilla is an online image optimizer uses a smart combination of best optimization and lossy compression algorithms in order to shrink JPEG and PNG pictures to the minimum possible size while keeping the required level of quality.