Heckyeah my PunyPNG now allows the max of 500 KB and uploads up to 75 files 🙂
The default is 150 KB and 15 files, but if you donate you get the increase.
PunyPNG, for me is one of the most efficient PNG compressors out there, first of all it’s online, so you can access it anywhere, and second, it’s really is pretty good at compressing compared to other compressors out there. See comparison chart on their website: http://punypng.com/about/comparison
PunyPNG website: http://punypng.com/