NWChem aims to provide its users with computational chemistry tools that are
scalable both in their ability to treat large scientific computational chemistry
problems efficiently, and in their use of available parallel computing resources
from high-performance parallel supercomputers to conventional workstation
clusters.

NWChem software can handle:
* Biomolecules, nanostructures, and solid-state
* From quantum to classical, and all combinations
* Ground and excited-states
* Gaussian basis functions or plane-waves
* Scaling from one to thousands of processors
* Properties and relativistic effects 

WWW: http://www.nwchem-sw.org/index.php/Main_Page