What are some alternatives?
When comparing Caesium Image Compressor and ImageOptim, you can also consider the following products
FastStone Photo Resizer - Convert and Rename images in batch mode Support JPEG, BMP, GIF, PNG, TIFF and JPEG2000
CodeKit - CodeKit allows you to optimize the performance of your website by automatically and efficiently compiling a variety of popular languages.
XnConvert - XnConvert is an easy image converter for graphic files, photos and images available on Windows...
Transmit - Transmit is an FTP client for Mac OS X and Mac OS Classic (which is unsupported).
pngquant - command-line utility and library for lossy compression of PNG images
TinyPNG - Make your website faster and save bandwidth. TinyPNG optimizes your PNG images by 50-80% while preserving full transparency!