  We study the final architecture of planetary systems that evolve under the
combined effects of planet-planet and planetesimal scattering. Using N-body
simulations we investigate the dynamics of marginally unstable systems of gas
and ice giants both in isolation and when the planets form interior to a
planetesimal belt. The unstable isolated systems evolve under planet-planet
scattering to yield an eccentricity distribution that matches that observed for
extrasolar planets. When planetesimals are included the outcome depends upon
the total mass of the planets. For system masses exceeding about one Jupiter
mass the final eccentricity distribution remains broad, whereas for lower mass
planetary systems a combination of divergent orbital evolution and
recircularization of scattered planets results in a preponderance of nearly
circular final orbits. We also study the fate of marginally stable multiple
planet systems in the presence of planetesimal disks, and find that for high
planet masses the majority of such systems evolve into resonance. A significant
fraction lead to resonant chains that are planetary analogs of Jupiter's
Galilean satellites. We predict that a transition from eccentric to
near-circular orbits will be observed once extrasolar planet surveys detect
sub-Jovian mass planets at orbital radii of 5-10 AU.
