Youtube video on Magnetic Resonance using earth-field NMR experiment. The technology employed is different but the discussion is, particularly the theoretical description is appropriate to the Teachspin device http://www.youtube.com/user/magritek
A nice simulation from the UF's Center for Safety, Simulation and Advanced Learning Technologies. It provides you with a better visual of how NMR works. You'll need an Adobe Shockwave so you iPad/iPhone may not work and or you'll need to add it to you browser. http://vam.anest.ufl.edu/simulations/nuclearmagneticresonance.php