How many bands can you see in one day? Rise to the challenge at these music festivals.

July 18: The ninth annual Ozzfest at Nissan Pavilion with Ozzy Osbourne and Black Sabbath, Judas Priest (with Rob Halford), Slayer, Dimmu Borgir, Superjoint Ritual, Zakk Wylde's Black Label Society, Slipknot, Hatebreed, Lamb of God, Atreyu, Every Time I Die, Lacuna Coil, Bleeding Through, Unearth, God Forbid and many more.

Aug. 4: The 10th annual Vans Warped Tour, with Nissan hosting the perennial skate-punk summer festival. Featuring Bad Religion, New Found Glory, Good Charlotte, NOFX, Simple Plan, Taking Back Sunday, Yellowcard and more than 20 other bands sharing six stages.

Aug. 10: The third annual Projekt Revolution at Nissan features rock-rap survivors Linkin Park, nu-metalists Korn, rapper Snoop Dogg (with a band, the Snoopadelics), screamo band the Used and ska band Less Than Jake.

Aug. 12, 13: Lollapalooza at Merriweather Post Pavilion. Lollapalooza expands this year to two days and returns to the wider variety of music genres it helped pioneer. Day One is headlined by Morrissey, Sonic Youth and PJ Harvey and features Modest Mouse, Le Tigre, Black Rebel Motorcycle Club, Broken Social Scene, the Walkmen, Wolf Eyes, Danger Mouse, the Datsuns, Sparta, Mike Watt & the Secondmen, Carina Round, the Living Things, Ross Golan & Molehead and the Dresden Dolls; Day Two is headlined by the String Cheese Incident, the Flaming Lips and Wilco, with support from Michael Franti & Spearhead, Gomez, the Polyphonic Spree, Elbow, Sound Tribe Sector 9, the Coup and Wheat.