Shrink Me - Compress images with one drag / click
TinyJPG - Compress JPEG images with perfect quality and file size
Aerate for macOS - Ridiculously good lossless image compression
Watermark.ink - Online Photo Watermarker
Squash 2 for Mac - The easiest way to compress and optimize images for the web
TinyPNG - Make your website faster and save bandwidth. TinyPNG optimizes your PNG images by 50-80% while preserving full transparency!