Google Analytics may be free, but it is still based on proprietary technology - which means you only ever get reports on the things that Google thinks are necessary and some of those reports are aimed at people using Google's other services (managing campaigns on AdWords, for example). Further, using Google Analytics means that you're tied to Google's TOS. Enter Piwik, which aims to be an open source alternative to Google Analytics. It is closely affiliated with OpenX, the open source ad server alternative to Google Ad Manager [Ed: which we just started using on RWW].

While OpenX has been around a while and has good traction, Piwik is fairly new and under the radar. It surfaced first as PHPMyVisites and is only at version 0.1.5, which is a sign that it is still for the highly committed.

Piwik originates from France and almost all the attention so far has been from outside USA. It seems to be catching on in Japan and China, as well as in Europe. The team responsible for Piwik seems to be made up of interns from big companies such as Amazon, Intel and Google