What are some alternatives?
When comparing FileOptimizer and ImageOptim, you can also consider the following products
Caesium Image Compressor - Compress your pictures up to 90% without visible quality loss.
CodeKit - CodeKit allows you to optimize the performance of your website by automatically and efficiently compiling a variety of popular languages.
pngquant - command-line utility and library for lossy compression of PNG images
Transmit - Transmit is an FTP client for Mac OS X and Mac OS Classic (which is unsupported).
ImageMagick - ImageMagick is a software suite to create, edit, and compose bitmap images.
TinyPNG - Make your website faster and save bandwidth. TinyPNG optimizes your PNG images by 50-80% while preserving full transparency!