Outkast is an Atlanta based rap duo who are heavily influenced by the 70's soul funk sound. If anything I would like to compare them to the Beastie Boys of the South. Outkast has a sound that is outside of the box if you will, they do not look like they stereotypical rap artist, you will not see them wearing throwback jerseys or carrying guns or acting violent.
Outkast along with Goodie Mob which includes Cee-Lo form the Dungeon Family. They have been working with each other for years and often appear on each others albums or remixes. Other artist Outkast has worked with on a semi-regular basis are Erkah Badu, The Roots, Common.
Look for these songs:
Wheels of Steel, Jazzy Belle, Ms Jackson, Elevators, Rosia Parks, Neck of the Woods, The Whole World, BOB, Art of Story Telling.
If you like Outkast might as well get Black Eye Peas, De La Soul, Tribe Called Quest, Del the Funky Homosapian, Jurassic 5.