I like easy-thumbnails and use it often in my Django projects, but I wished for a long time that its PIL generated thumbnails would be smaller. That’s why I wrote image-diet, a drop-in extension for those easy-thumbnails users who use file system for storing images. Images remain visually the same, but can be significantly smaller (mine by more than 50% but your mileage my vary).
image-diet was inspired by ImageOptim and Trimage and I’m grateful to authors of both. It uses jpegtran, Jpegoptim, Gifsicle, OptiPNG, AdvanceCOM PNG and Pngcrush to do the heavy work of squeezing redundant bytes. Getting them should be easy as they are part of Ubuntu distribution and can be installed on Mac with brew. For more information please check documentation or ask.
I would love to hear any comments and ideas you may have, even more so if you try it.