There is an excellent 2CD boxed set from Chess of songs written by Willie Dixon, recorded by the original artists. It includes everyone you would expect, Muddy Waters, Howlin Wolf, Bo Diddley and a couple dozen lesser known Chess artists. It is not only a good source for his songs but a great sampler of Chicago blues.

For another, less commercial, side of Willie Dixon, check out his album "Mighty Earthquake and Hurricane." The songs tend to be more cynical looks at society, religion and death. Less memorable but very interesting.