Tools
SExtractor
SExtractor is a program that builds a catalogue of objects from an astronomical image. Although SExtractor does perform galaxy shape measurements (A_IMAGE and B_IMAGE), these parameters are not accurate enough to perform lensing measurements:
http://terapix.iap.fr/rubrique.php?id_rubrique=91/
DS9
SAOImage DS9 is an astronomical imaging and data visualization application. DS9 supports FITS images and binary tables, multiple frame buffers, region manipulation, and many scale algorithms and colormaps.
http://hea-www.harvard.edu/RD/ds9/
Imcat
The imcat software was developed by Nick Kaiser to do faint galaxy photometry and to perform weak lensing studies:
http://www.ifa.hawaii.edu/~kaiser/imcat/
Im2shape
A weak lensing shape measurement method developed by Sarah Bridle. This method is based on a Bayesian approach and galaxies are parameterized as a sum of gaussians, convolved with a psf which is also a sum of gaussians:
http://www.sarahbridle.net/im2shape/
Multidrizzle
Software to combine single HST exposures by the drizzling method:
http://stsdas.stsci.edu/pydrizzle/multidrizzle/
Lenstool
A gravitational lensing software developed by Jean-Paul Kneib for modeling mass distribution of galaxies and clusters (strong and weak regime)
http://www.oamp.fr/cosmology/lenstool/
The IDL Astronomy User's Library
The IDL Astronomy Users Library is a central repository for low-level astronomy software written in the commercial language IDL:
http://idlastro.gsfc.nasa.gov/
HST ACS Point Spread Function models
PSF models developed by the COSMOS team for the ACS that account for the breathing of the HST:
http://www.astro.caltech.edu/~rjm/acs/PSF/
Weak Lensing review article
An excellent review article on Weak Gravitational Lensing by Matthias Bartelmann and Peter Schneider: