I recently came across some extremely informative online resources for learning the basics of (nuclear) magnetic resonance. The first (via Agilent's Spinsights.net blog) is an online simulator that is nicely introduced in a series of four YouTube tutorials (see below). The simulator allows you to demonstrate such concepts as RF excitation, the rotating frame of reference, relaxation and even a 1D gradient for spatial encoding. If you are brand new to MR then you might need some assistance in understanding things for yourself, and I would think this tool (and the supporting tutorials) would be best used by an instructor in a class, but I don't want to dissuade you from taking a stab on your own. Watch the videos first (see below), then check out the simulator. (You can also find technical info and links to the tutorials at www.drcmr.dk/bloch.)
The other resource I found just about blew me away, not so much for the NMR lectures themselves, as good as they are, but because they are part of an extensive biophysics course covering everything from electromagnetic radiation to flow cytometry and sedimentation methods! The lectures are by Yair Meiry, a fellow who is apparently now working as a skydiving instructor in Canada (assuming my Internet sleuthing has improved since yesterday's attempt to divine the Scandinavian country of origin of another YouTube video). Channeling his inner Garrett Lisi, perhaps? I know I'm impressed.
Bloch Equations Simulator Tutorials
Part 1: Introduction to the Bloch Simulator made for basic MRI and NMR education
Part 2, NMR/MRI-education: Simple spin dynamics explored using the Bloch Simulator
Part 3, NMR/MRI-education: Spin-echoes explored using the Bloch Simulator
Part 4, NMR/MRI-education: K-space imaging in 1D explored using the Bloch Simulator
Link to the simulator itself, which runs inside your web browser: www.drcmr.dk/BlochSimulator/
PS Another Bloch equations simulator for Mac OS X: Spin Bench. Thanks to Miki Lustig for the tip.
Understanding NMR, by Yair Meiry
Part 3 (solving problems for a formal class)
A link to the parent biophysics course: https://sites.google.com/site/yairmeiry/home