I finished a new version today. Now the hierarchical clustering works twice(!) as fast. This is achieved because the distance-matrix which is generated internally is symmetric. So I only need to calculate one half of the possible combinations.
More improvement is possible. But I gave up on that today. Too complex.
I also started to work out the details for a K-Means algorithm on the Airport this weekend. On paper it looks sensible and I beleive it should work as I wrote it down. Now I only need to beam my scribblings onto the harddisk. And hope it all works ;)