Conservation of momentum in the center of momentum frame has a very simple geometry. The two objects simply reflect... the angle of incident equals the angle of reflection.
This angle is measured from the line of centers.
Included are 30 diagrams of momentum collisions for some nice angles plus the Mathematica 6 code I used to generate the images.
This is the pay version for commercial use or to show appreciation for the work. For classroom use, see my free version.