The original plugin that started it all, the EWWW Image Optimizer can use freely available optimization tools directly on your web server OR use the Compress API + our Easy IO CDN to compress & resize JPG, PNG, and GIF images as well as optimize SVG & PDF files. Available on GitHub and WordPress.org.
Now you can get all the speed boosting tools that I use personally, in one handy package. Includes page caching, JS/CSS optimization tools, ability to disable unused JS/CSS, Google Font optimizer, CDN rewriter, and more.
A plugin for WordPress that lets you optimize images in Amazon S3 buckets, and integrates with the EWWW IO plugins to provide full compression capability.
The Standalone Image Optimizer lets you optimize your images from the command line with no dependencies on WordPress. Read more about it at GitHub.