As a musician and band director I have been very familiar with copyright laws all my life.
As for Dropbox - it looks pretty cool. Right now I use my flash drive to keep files I want to transport. My classroom is performance driven - not much time for the kiddos to play on computers. I do like to share videos of past performances (like - here's what you did at halftime Friday night, now let's fix it!) before and after school hours.