I �m also searching for a song related to that subject. I googled and I found a few in Spanish but I don �t know which one is the best. I wonder if you could suggest one that you have already used. 

Many thanks in advance for your help. 

Hugs 

I definitely recommend you "Skalipso" by "Las Pastillas del abuelo" and "Me est�s atrapando otra vez" by Andr�s Calamaro. These two are the best ones though they have some colloquial expressions (not too many) your students may find difficult to understand. In my point of view, "Skalipso" is better if you hope for a debate about the subject after listening to the song.

I couldn �t find any useful worksheet for the subject, but maybe you can make your own worksheet related to the song you choose. 

Hope you find this useful!