Forty-three years ago today, a bunch of fed-up drag queens, hustlers, and assorted gay misfits at the Stonewall Inn in New York turned the tables on a harassing police raid. That resistance gave rise to a series of riots and ultimately to the birth of the modern gay activist movement. It seems like a long time ago, and things (laws and minds) have changed, but we still have a long way to go, and a lot more irrational fear, hatred, bigotry, and misconceptions to fight.
But today, we thank the brave men and women at Stonewall and the ensuing riots for saying, "ENOUGH. I AM A HUMAN BEING AND I DEMAND TO BE TREATED AS ONE!"
There is a very nice, informative Wiki entry about the riots and the history leading up them: