April 7, 2010 update

It seems that piwiki has a Plugin for Click Heatmap. I will try to install that. What I didn´t see is "Event Tracking" see Event Tracking at Google Analytics.

What I also saw is that the Extension:UsabilityInitiative, that is active at Wikipedia, uses Click Tracking as part of the Beta rollout.

What I like is the programming language R which is able to W:Cluster analysis. We have got a Wikibook Wikibooks:Data Mining Algorithms In R. But clustering works with numbers, not with click paths. I wonder if it is possible to transform click paths into numbers.

Thanks, Goldzahn. I updated the Piwik page with this information. I'm sure it's possible to do cluster analysis on click paths.