Here is a simple planet complete with canals and lakes. Everything works from two Power Fractals, one for the main shape and another to deform it into a more interesting coastline. The rivers, mountains, hills and grass coverings are all derived and controlled by the same two PF's. I'll release this into the wild when I've sorted and tweaked it some more.
Crits VERY welcome indeed, bring it on ;o) Do realise that this image is only very simply textured but it is intended as a start point ....
Enjoy
Richard