Clusters as Tracers of Large-Scale Structure
  By virtue of their high galaxy space densities and their large spatial separations, clusters are efficient and accurate tracers of the large-scale density and velocity fields. Substantial progress has been made over the past decade in the construction of homogeneous, objectively derived cluster catalogs and in characterizing the spatial distribution of clusters. Consequently, the constraints on viable models for the growth of structure have been refined. A review of the status of cluster-based observations of large-scale structure is presented here, including discussions of the second and higher order moments, the dependence of clustering on richness (mass), recent and new measurements of bulk flows, and a new constraint on the cluster mass function in the range 0.7 < z < 1. 
Marc Postman