Speakerboxxx/The Love Below
This will not shock the cognoscenti. Outkast is the most innovative rap group around today. They rap about real life and real feelings without having to go gangsta. The production is impeccable, the jams borrow heavily from Parliament and Prince, and even the skits (de rigeur, and silly at best, on most rap albums) are worth listening to. Andre 3000 and Big Boi deliver a solid rap album on CD1, and venture into some more experimental works on CD2.
Big Boi dominates CD1 obviously, while Andre commands the second disk, but they are both well represented on both disks. While Andre is clearly the visionary and the musical and production guru, Big Boi is no slouch himself and Andre would likely be worse for not having that balance. Even though disk one is more "conventional" hip hop, there's plenty of experimentation there as well, taking cues from The Roots, Dan the Automator, and George Clinton.
Hot Spots: GhettoMusick, Bust, Flip Flop Rock, Vibrate, Behold a Lady, She Live In My Lap, Love Hater