With this applet, you can view colorspaces in slices along three variables: Saturation, Lightness, and Hue.
Holding one variable steady - for example, Saturation, you can then view a 2D "slice" of possible Light/Hue combination values one the one-dimensional plane of Saturation.

This blog post written by Brian Cort, the developer and visual artist who made this app, explains basic color theory and color spaces HERE.