Also, check out the relatively detailed cyanotype toning section of the Christopher James book. Lots of goodies in there.

My favorite that I have discovered myself is Ilford Multigrade paper developer. Replaces all the blue with a light tan and leaves the whites white. I have tried various dilutions, including straight, and they all have the same effect. I am using Arches watercolor 90# cold press. Can't wait to try this with some suitable subject matter for tan and white...