I have posted several tutorials for mel aready in this MEL forum, I guess that is where I will post any new ones. Just look for any of my posts in Mel Scripts & Programming, I have already got a few in here.

"Why Should you learn MEL . . ." in Maya chat is a good one if you do not yet understand how to create shelf icons and commands . . . it is a real good start point, because it demonstrates how you can learn MEL and apply it even before you are writing code!