Communities and miscellany

• ##canvas on Freenode (part of the reason for this list)
• Canvas Articles at hacks.mozilla.org
• Mozilla Developer Network: Canvas (more links to be harvested here)

Tutorials

• Mozilla Developer Network: Canvas tutorial
• HTML5 Canvas Tutorials
• HTML5 Rocks
• Diagramo: Documentation Resources

References

• Nihilogic: HTML5 Canvas Cheat Sheet

Examples and applications

• js1k
• html5-canvas-graphics
• HTML5 Canvas demos by Kevin Roast
• Splashnology: 15 Awesome Free JavaScript Charts (note: the software freedom advertised in the post was disputed in the comments)
• Diagramo, a gratis proprietary UML editor
• The jsUML2 editor, another UML editor, based on the FOSS library by the same name

Libraries, frameworks, and engines

• EaselJS
• Suburban Glory: Review of HTML5 Canvas Libraries
  • jCanvaScript
  • Fabric.js
  • CAKE (LIE!!)
  • doodle.js
• Isogenic Engine (warning: large price tag)
• jsUML2, a UML library