Is there a computer program that simulates biology on a molecular level? Software that has rules that simulates the rules of molecular-biology?
There is a recent paper that introduced the first molecular-level whole-cell simulation.
Karr, J.R., Sanghvi, J.C., Macklin, D.N., Gutschow, M.V., Jacobs, J.M., Bolival, B., Assad-Garcia, N., Glass, J.I., & Covert, M.W. (2012). A whole-cell computational model predicts phenotype from genotype. Cell 150:389-401 DOI: 10.1016/j.cell.2012.05.044
The authors combined 28 different sub-modules of various biological processes from the literature. Each one operates at the level of macromolecules, although models them in different ways: some by ODEs, some by logic; some by agent-based approaches. If you want to fool around their code is available online and I wrote a basic introduction/summary of the paper.
Here are some related bio.SE questions motivated by that model:
NAMD is a molecular simulation software system with an extensive, active community of researchers
it has a slick visualization package called VMD