OxiPNG and Pngout

One thing that had stuck with me from reading Coding Horror, is that you can increase the speed of your website with free bandwidth. In fairness, it’s not free bandwidth, it’s reducing the file size of the files that you’re hosting, so it’s faster to download. The Zopfli article above is the more recent one - the first was regarding pngout (article). Both pngout and zopfli can reduce the size of files - specifically in this case, PNG files.