TinyPNG: Lossy compression for PNG that preserves full transparency.
I don't mean this as a dig at the developers of this particular site because my annoyance is more of a cumulative thing as opposed to being about this website in general, but IMO this is yet another website that does one simple thing that should be a library (or at the very least a documented web api) and not a website.Websites of 2012, I am disappoint.