Ear plugs for live musc.

Yup the blond version.  The Wilson sisters have been playing loud for 40 some years.  Dunno how they can still hear. 
There is a line from Good Morning Vietnam where Robin Williams (Adrian Kronaur) asks a GI what he wants to hear.  The GI says, "I don't care, just play it loud!".  Williams asks, "What do you do?".  GI says, "I'm in artillery."

Another vote for the Etymotic earplugs. The ER-20 model is very reasonably priced and, like larryrs, I've used them for years for motorcycle riding where, as in listening to music, you want the full spectrum of sound of what's around you. 

They also have the advantage of coming in different sizes. One of my ear canals is larger than the other so I've always bought one pair of the standard size and one pair of the large size, split the pairs and had two pair that will work for me.

One other tip is to buy an eyeglass cord, the kind that are designed to let you take off your glasses and let them hang around your neck. The ends slip perfectly onto the Etymotic earplugs, meaning you can take them out and still have them hanging around your neck, ready to use again and lowering the risk of losing them.

 When you crank it on the stage, you can mask imperfections of performance. Many rockies do that.

I found these to be effective: www.erasers.net

If you go to a hearing aid place, you can have soft rubber molds made of your inner ears. Etymotic makes little SPL discs attenuation discs (5-10-15-20 dB) that you then insert into the outer end of the molds. The discs attenuate all frequencies evenly (flat frequency response), so you don't get the muffled sound of most ear plugs. I've been wearing them since the mid-80's, for live shows and personal performances. It makes gauging dynamics (your volume in relation to the other musicians) a little difficult, but it's worth it.