The Reason Rally was an amazing convergence of 10 to 20,000 or more secularists. There are a whole range of videos that have been posted that gives a good flavor of the many wonderful people who made presentations.
Reason Rally - March 24 2012 Washington DC Richard Dawkins
Reason Rally, Prof. PZ Myers Speech
Bill Maher Video - Reason Rally 2012!
Eddie Izzard at the Reason Rally Wash. DC 3/24/2012 Part 1 of 3
Adam Savage at the Reason Rally
Nate Phelps at Reason Rally