Stanford University
Ccrma: Common Music Notation
This resource features information on notes, rests and many, many other basic music theory examples.
Music Theory
Music theory.net: Rest Duration
A wonderful resource for teachers and students! Gives examples and explanations of rests and how they affect the sound of a musical piece. Simple illustrations and explanations make this animated site easy to follow.
Music Education
Learning to Read Music: Types of Rests
This tutorial teaches students the different kinds and values of rests in music notation.