Free stuff* is always nice, right? Zopfli is really nice, now I just have to try the bread as hell.

Zopfli Optimization: Literally Free Bandwidth

$ time zopflipng -m democracy-for-sale.png test.png
Optimizing democracy-for-sale.png
Input size: 673908 (658K)
Result size: 411196 (401K). Percentage of original: 61.017%
Result is smaller

real	0m23,125s
user	0m18,019s
sys	0m0,052s

* comes at a slight computational cost.