There isn't much that can be done. What irks me more than the wait is the blasted TV and the shows on it in waiting rooms. I was waiting for a chemical stress test at the hospital and the wait is v. long after being injected with a...whatever it is...and I sat through morning game shows..ding, ding, hyperactive MCs, gushing contestants, ding, ding. Thought I was going to scream, but I was compensated by the technician for the longer than usual wait. I was given 2 $10 Walmart gift cards! Ding, Ding!
At another time a doc gave me a Walmart gift card for the long wait in his waiting room. I thought both those offerings acts of consideration.
I've also seen a sign "If you have been waiting for more than 15 minutes, please let the receptionist know." Nice touch!