Oh sweet jeezus! I hate that crap so much! Jeremy Clarkson (of the BBC's Top Gear) puts it best "Americans don't understand that the [left] lane is for passing! You drive slow in the fast lane and drive with your fog lights on when there is no fog! Where are you learning these driving habits?"
Every time someone is in the left lane and NOT passing I turn on my left blinker to kinda hint for them to get over, if they don't move I flash my headlights. I hate how people drive slow in the fast lane... worst place for this ever is on I-70 between Golden and Chief Hosa headed west- mainly because it's uphill and truckers are a**holes who want to try to pass while in low gear going up the mountain so everyone gets over into the left to try to pass them doing 55! ARG!