Some of the biggest names in rock will be making their way to Chicago this weekend for Lollapalooza.  The three-day festival gets under way today at the Windy City's Grant Park.  Acts on board for Lolla's 20th anniversary include Coldplay and Muse, who are both set to headline tonight's lineup.  Also on day one, the event's eight stages will feature performances from the Kills, Bright Eyes, Ok Go, Girl Talk, A Perfect Circle and more.  Eminem headlines Saturday's lineup along with My Morning Jacket, Patrick Stump, Lykke Li and Cee Lo Green, to name a few.  The Foo Fighters close the festival on Sunday, but not before the Cold War Kids, Arctic Monkeys, Best Coast, Cage the Elephant and others take the stage. For anyone who can't make it to the festival, Lollapalooza is teaming up with YouTube to broadcast the concerts online.  The webcast is set to start this afternoon at 2:30 Eastern and a full schedule can be found at YouTube.com/Lollapalooza.