Resizing.app - Image resizing has never been so simple with free online resizing.app. Convert, optimize, resize images with ease and for absolutely free.
Squash 2 for Mac - The easiest way to compress and optimize images for the web
ImageKit.io - Instant multi-platform image optimization
Image Resizer for Windows - Lets you resize images by right-clicking.
Gumlet - Gumlet is an end-to-end video streaming and image delivery platform
imgix Sandbox - Resize & process images in real-time w/ simple URL commands