Ralpha Image Resizer - High-speed image batch conversion tool
imgix - Real-time Image Processing. Resize, crop, and process images on the fly, simply by changing their URLs.
ImBatch - ImBatch is a batch image processor with a nice graphical user interface.
Cloudimage - Cloudimage.io is the easiest way to resize, store, and deliver your images to your customers through a rocket fast CDN.
Caesium Image Compressor - Compress your pictures up to 90% without visible quality loss.
Sirv - Dynamic image processing, hosting and rich-media for retailers and eCommerce.