ImageOptim - Faster web pages and apps.
TinyPNG - Make your website faster and save bandwidth. TinyPNG optimizes your PNG images by 50-80% while preserving full transparency!
FILEminimizer Pictures - FILEminimizer Pictures compresses JPEG photos, TIFF, BMP and PNG images and pictures by up to 98%.
Image Compressor by RedKetchup - Compress the file size of a PNG, JPEG, WEBP, or HEIC image online. Reduce the image dimensions based on KB or MB. Improve the quality of PNG compression with dithering.
Shrink O'Matic - Shrink O'Matic is an AIR application to easily (batch) resize (shrink) images.
TinyJPG - Compress JPEG images with perfect quality and file size