According to The Natural Beauty Workshop, Melt & Pour soap can be a lot of fun. As far as soap making methods go, this one probably offers the widest range of complexity. You can keep things easy by making a solid colored soap, or spice things up with layers, additives, and embedding. It all just depends on how much you feel like taking on.
This Grapefruit Eucalyptus Soap Bar recipe is about a medium as far as difficulty goes. It involves coloring and scenting two batches of base and layering them into their molds. The result is a pretty two-toned bar with a pleasant layered scent.