We present results from a weak lensing survey of a sample of 53 clusters of galaxies at $0.15 < z < 0.4$, selected based on their high X-ray luminosities. For each cluster, we measure the mass-to-light ratio out to a radius $R \sim (0.5-1.5) h^{-1}$ Mpc. By measuring the lensing masses of a large sample of clusters in a consistent way, we quantify the intrinsic scatter in $M/L$ and determine its average value for massive clusters. In the near future, an ongoing spectro-photometric and weak lensing survey of a supercluster region in Aquarius will extend $M/L$ measurements to much larger radii and explore its dependence on scale and environment.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html