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.
M. Vasconcelos, P. Mauriz, E. Albuquerque, E. da Silva, and V. Freire. APPLIED SURFACE SCIENCE, 234 (1-4):
33-37(2004)9th International Conference on Formation of Semiconductor Interfaces
(ICFSI 9), Madrid, SPAIN, SEP 15-19, 2003.