animation101: A Simple Method for creating Walk Cycles
Very good explanation on how to easily make a walk cycle look realistic.
Walk cycles based on motion capture from 40 men and 40 women. It allows you to set various parameters to see the different walk styles.
Walk Cycle Chart
Alonzo von Threet
Good chart explaining the various steps in a walk cycle.
Humanoid Walk Cycle
Images showing many steps in both a normal walk cycle and a run cycle.
Very good explanation on the walk cycle.
Preston Blair Walk Cycle
Drawings of several types of walk cycles, e.g. normal, run, sneak, shuffle, etc.
Animating a walk cycle
Sample animations of different walk cycles, like normal, sneak, shuffle. The article also talks about the character's attitude and how it affects the body position.