I had a discussion with Saskia a looong time back about MRI, and I learnt a little about how MRI machines work, in the process. Anne encouraged me to blog on this new-found knowledge, and after a LOT of procrastination, I've finally managed it. Hope you like it: it's layman level, and not too badly written (I hope).
Here it is: The Physics of MRI
If you find any faults, or find some section unclear, or have any critcisms at all (even positive ones ;-) ), do comment.