Cassandra is an open source Monte Carlo package developed in the Maginn group at the University of Notre Dame. It is released under the GNU General Public License.
Cassandra is capable of simulating any number of molecules composed of rings, chains, or both. It can be used it to simulate small organic molecules, oligomers, and ionic liquids.
It uses OpenMP parallelization and comes with a number of scripts, utilities and examples to help with simulation setup.