Coldcut, Buck 65, Sage Francis.

Also, if you care mostly about the lyrics, some other types of music you should look into are reggae or ragga. Barrington Levy, Buju Banton and the like. Very melodic and relaxing with a strong message.

If you speak any French, you may consider French hip-hop. There are many French artists who criticize the outspoken mainstream contrast to the American hiphop scene. The lyrics have much more meaning since many of the rappers care more about message than money and as a result, remain in the banlieus of France.