Check out my Biology Education Software FAQ, which you can download
from ftp.zoology.washington.edu /pub/doc, or which will be reposted
here real soon now. I list quite a bit of simulation software. Also,
try ordering the BioQuest CD which has lots of nice simulation software
for teaching biology (someone's borrowing my copy right now but the
address is in the FAQ).
Good luck,
Eli Meir
Dept of Zoology, Univ of Washington
meir at zoology.washington.edu