For information on extension of the CHARMM biomolecular force fields to drug-like molecules.  Parameter optimization power point presentation and tgz file of example inputs for parameter optimization from the MMTSB/CTBP summer workshop, 2006 are linked to the Pittsburgh Supercomputing Center tutorial and example inputs.

http://www.psc.edu/general/software/packages/charmm/tutorial/index.html

Additional tutorials and introductions to CHARMM

http://www.ch.embnet.org/MD_tutorial/

http://www.geocities.com/gschreckenbach/charmm_DIR/charmm.html

http://www.sinica.edu.tw/~scimath/msi/insight2K/charmm_principles/CHARMm_PrinTOC.doc.html