Imagify - Optimize and resize images online and through your CMS.
Ralpha Image Resizer - High-speed image batch conversion tool
Cloudinary - Cloudinary is a cloud-based service for hosting videos and images designed specifically with the needs of web and mobile developers in mind.
ImBatch - ImBatch is a batch image processor with a nice graphical user interface.
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.