  We describe an interactive computer program that simulates Stern-Gerlach
measurements on spin-1/2 and spin-1 particles. The user can design and run
experiments involving successive spin measurements, illustrating incompatible
observables, interference, and time evolution. The program can be used by
students at a variety of levels, from non-science majors in a general interest
course to physics majors in an upper-level quantum mechanics course. We give
suggested homework exercises using the program at various levels.
