Overrated (Because I Wasn't There)

Rock the Bells, Jones Beach. Nas, ATCQ, De La, Ghostface & Raekwon, Meth & Red, Mos Def, Afrika Bambaataa, the Cool Kids, Spank Rock.

-- Talib Kweli came out during Mos Def's set and they had a Black Star reunion. People lost their shit.
-- Jay-Z came out during Nas' set and performed "Black Republican" [and, according to Billboard.com, "Success"] with him. Everyone lost their shit.
-- Busta Rhymes came out during A Tribe Called Quest's set, right at the point in "Scenario" when Q-Tip says, "Yo Mr. Busta Rhymes, tell him what I did." People in China, Estonia, and Long Island lost their shit.

Slick Rick, EPMD, and Pharoahe Monch also stopped by. [Source]