Gil Scott-Heron is one of the great recording artists of the 20th century. It is a shame that most people know almost nothing about him.
He work is almost always interesting and I would recommend (almost) all of his albums. If you are unfamiliar with his work then this compilation album is a very good place to start.
Gil Scott-Heron draws on a wide range of influences: the music of John Coltrane, the blues, the oral traditions of the American South and many others to create fantastic music in a variety of different styles from spoken word/rap to (almost) soul.
He is perhaps best known for his searing political (and personal) lyrics that are often so good that they can be read as poetry. However, he is also an excellent musician and the music always complements his lyrics.
If you want to know more about him then I recommend trying to catch the Don Letts documentary when it is next shown on BBC3 or BBC4. Be warned his life is something of a tragedy - problems with addiction, particularly crack cocaine, and the associated jail time have dominated his later years (particularly ironic as two of his most famous songs - The Bottle & Angel Dust - are tirades against alcohol and drugs).
However, none of these problems detract from his music - he has been my favourite artist for nearly 20 years and I suspect he will be my favourite for the next 20.