The real music festival is this weekend... Lollapalooza in Chicago. The lineup has gotten more recognizable at least for me since most of these are Alt, there are a few rap and pop here as well.
Friday's noticeables:
Eminem (everyone knows him), Arctic Monkeys, Lorde (Royals), Zedd, Broken Bells, Interpol, Phantogram, Chvrches, Portugal the Man, Iggy Azelea

(HATE) , AFI, The Kooks, Rudimental, Hozier (Take me to Church), Bombay Bicycle Club, Kodaline, Royal Blood, Cash Cash, etc...
Saturday's noticeables:
Outkast (Remember them?), Calvin Harris (

), Foster the People (Pumped up Kicks), Krewella, Nas, Spoon, Head & the Heart, Cut Copy, Fitz & the Tantrums, Grouplove (Tongue Tied), Manchester Orchestra, The Temper Trap, Vance Joy, Smallpools, Papa, Joywave, etc...
Sunday's noticables:
Kings of Leon (You know I could Use Somebody), Skrillex, Childish Gambino, Cage the Elephant (Shake me down), Young the Giant, Chromeo, The 1975, The Airborne Toxic Event, RAC, KONGOS (Come With me Now), NONONO, Gemini Club, Bleachers, Bear Hands, etc...
Hopefully you can recognize some of these.