Look up Tim Lee from the Cato Institute. I think he has written on this topic. I think the standard libertarian position on net neutrality is that it's no good. Personally, I don't have the technical knowledge to really comment, though once at what might be called a libertarian boot camp, I came up with the slogan "surf at your own speed" in an exercise to come up with promotions for net nonneutrality.

Also, see this podcast: http://www.econtalk.org//archives/2009/01/eric_raymond_on.html

Toward the end (i think) they get into the issue. I can't remember what Raymond says, but IIRC, he takes a nonneutrality position while not sound like the standard libertarian position. It's an interesting podcast throughout, however, and you should listen to the whole thing. All of you.

edit: It was Tim Lee, not Tim Butler: http://www.cato.org/people/timothy-lee