Generalized single linkage clustering (GSL)
GSL is a method for nonparametric clustering described in the following article:
W. Stuetzle and R. Nugent
A generalized single linkage method for estimating the cluster tree of a density.
Journal of Computational and Graphical Statistics, 2009 (to appear)
PDF Online supplement
The online supplement has all the Latex source, R code, and data to generate the paper, as well as an R package gslclust implementing GSL. In case you don't want to bother with unpacking, here is a link to gslclust.
To try gslclust on a PC, download the package. Then open a Command Prompt window, cd to the directory holding the package, and install the package by issuing the DOS command "R CMD install gslclust". You can find R code illustrating the use of gslclust here.