  The Red-Sequence Cluster Survey (RCS) is a 100 square degree galaxy cluster
survey designed to provide a large sample of optically selected clusters of
galaxies with redshifts 0.1<z<1.4. The survey data are also useful for a
variety of lensing studies. Several strong lensing clusters have been
discovered so far, and follow up observations are underway. In these
proceedings we present some of the first results of a weak lensing analysis
based on 24 deg^2 of data. We have detected the lensing signal induced by large
scale structure (cosmic shear) at high significance, and find
sigma_8=0.79+-0.08 (for a CDM cosmology with Omega_m=0.3,\Omega_\Lambda=0.7,
h=0.7). Another application of these data is the study of the average
properties of dark matter halos surrounding galaxies. We study the lensing
signal from intermediate redshift galaxies with 19.5<R_C<21 using a
parameterised mass model for the galaxy mass distribution. The analysis yields
a mass weighted velocity dispersion of <sigma^2>^{1/2}= 111+-5 km/s. In
addition we have constrained for the first time the extent of dark matter
halos, and find a robust upper limit for the truncation parameter s<470 h^{-1}
kpc (99.7% confidence). A preliminary analysis also excludes a simple
``prediction'' of lensing according to Modified Newtonian Dynamics (MOND) at
high confidence.
