To avoid the “hearing-loss panic” that was induced by the last concert I attended, I have looked around for a good set of earplugs. I have decided to pick up a pair of ER-20 HI-FI earplugs from Etymotic Research which are designed to attenuate the sound by 20dB without coloring the sound. So, in theory, unlike most earplugs I have tried, they should simply reduce the volume of the music without making it sound like shit (unless it was shitty to start with :P). I placed an order for a pair (they were only 10 bucks) and will let you know how they work after the next concert.
I came across this company when looking for a new set of headphones, and read many good reviews of their ER-4P earphones. Supposedly these earphones are like a set of earplugs that also happen to have an amazing set of earphones integrated into them, so you not only don’t hear much background noise, but you also get great frequency response. They are a little out of my price range at $330, but perhaps one day soon I will get a pair….