This is an exercise that I developed to better train the picking hand, but I knew that if I was going to devise and exercise that was meant to do this, that it would also have to be attractive sounding. Why? Because general exercises cause the learning guitarists to speed up, when they are not prepared for certain speeds. However, if something sounds good, then it will sound good even at slow speeds, so they won't care how fast they are playing it and will really take the time to get it down.
I'm not sure how you would classify this exercise but it certainly has a dreamlike structure to it. Almost a Fantasia. Anyways, check it out and the tablature is at http://www.guitarticles.blogspot.com