Instagram - Instagram is a mobile, desktop, and Internet-based photo-sharing application and service that allows users to share pictures and videos either publicly, or privately to pre-approved followers.
Optimage - Advanced image optimization tool
Manual Camera for iPhone - Custom exposure for your iPhone camera
ImageOptim API - Web service for image compression
Pixlr - Pixlr® makes it easy to transform everyday images into stunning works of art.
Imagify - Optimize and resize images online and through your CMS.