SAPT is a collection of computer codes designed to implement the many-body (body = electron) version of Symmetry-Adapted Perturbation Theory for intermolecular interactions. This code has been extensively used in studies of intermolecular forces. For a description of SAPT see: B. Jeziorski, R. Moszynski, and K. Szalewicz “Perturbation Theory Approach to Intermolecular Potential Energy Surfaces of van der Waals Complexes”, Chem. Rev. 94, 1887-1930 (1994).
The Computational Chemistry Comparison and Benchmark Database (CCCBDB) contains links to experimental and computational thermochemical data for a selected set of gas-phase atoms and molecules as well as tools for comparing experimental and computational ideal-gas thermochemical properties.
PyQuante is an open-source suite of programs for developing quantum chemistry methods. The program is written in the Python programming language, but has many "rate-determining" modules also written in C for speed.