Canvas Pocket Reference provides both a tutorial that covers all of the element's features with plenty of examples and a definitive reference to each of the Canvas-related classes, methods, and properties.
You'll learn how to:
Draw lines, polygons, and curves
Apply colors, gradients, patterns, and transparency
Use transformations to smoothly rotate and resize drawings
Work with text in a graphic environment
Apply shadows to create a sense of depth
Incorporate bitmapped images into vector graphics
Perform image processing operations in JavaScript