http://www.bell-labs.com/news/2000/may/11/1.html [Broken] has a number of links (bottom of the page) very relevant to observational studies of the distribution of dark matter. In particular, the last three links: http://dls.het.brown.edu/, a programme to create maps of the distribution of dark matter, across seven 4 square degree fields, using weak lensing (shear); this technique relies on large numbers of galaxy images and statistical analyses. Among the results are dark matter filaments. The data are publicly available, so anyone who wants to test an alternative cosmological model doesn't have to fight for scarce big telescope time. http://www.bell-labs.com/org/physicalsciences/projects/darkmatter/darkmatter.html [Broken], a set of webpages which describes the strong and weak lensing techniques. I found the strong lensing results, from one cluster, particularly interesting ... "The majority of the dark matter is distributed broadly and smoothly in the cluster, covering a region on the sky more than 1.6 million light-years across. The mass of the individual cluster galaxies appears as pinnacles on this mountain of dark matter mass. Overall, the dark matter in the cluster outweighs all the stars in the cluster's galaxies by 250 times as shown in the mass contour plot above. We know that most of the mass is not attached to the individual galaxies in clusters." http://www.bell-labs.com/news/1997/january/15/1.html [Broken], a PR.