, Jamie Foxx and Forest Whitaker are among the celebrities joining three presidents this week to mark the of the .
Soledad O'Brien and Hill Harper will host the "Let Freedom Ring" commemoration of Martin Luther King Jr.'sspeech. President Barack Obama and former presidents Bill Clinton and Jimmy Carter will serve as keynote speakers at the tribute.
Georgia, who spoke at the 1963 March on Washington, will also speak at this year's march, along with Winfrey, Foxx and Whitaker.
Winfrey and Whitaker are starring ina civil rights-era film about a man who served for seven presidents as a White House butler.
Musicians including LeAnn Rimes and BeBe Winans are scheduled to perform.
Open to the public, the "Let Freedom Ring" ceremony kicks off at 11:00 a.m. at the Lincoln Memorial on Wednesday.