What are some alternatives?
When comparing TinyPNG and ImageOptim, you can also consider the following products
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).
PNGGauntlet - -Combines PNGOUT, OptiPNG, and DeflOpt to create the smallest PNGs
CodeKit - CodeKit allows you to optimize the performance of your website by automatically and efficiently compiling a variety of popular languages.
JPEGmini - JPEGmini - The Photo Optimization Tool Trusted by Tens of Thousands Image Perfectionists
TotalTerminal - TotalTerminal is a plugin for Terminal. app which provides Quake-style terminal window available on keyboard shortcut.