Galactic Interaction Simulations
Joshua Barnes:
http://www.ifa.hawaii.edu/faculty/barnes/transform.ht
ml
John Dubinksi:
http://www.cita.utoronto.ca/~dubinski/nbody/
Chris Mihos:
http://burro.astr.cwru.edu/models/models.html
Bob Berrington (Wyoming):
http://physics.uwyo.edu/~rberring/
There are others