SVG and canvas
Numerous people have suggested that SVG and <canvas> are competing technologies. They are not. SVG provides retained mode graphics and <canvas> provides immediate mode graphics. A lot of use cases can be addressed by either, some are easier to do with one of them and some can only be done by one of them.
Ideally this page would list those use cases. Philip?
http://lists.w3.org/Archives/Public/public-html/2007Nov/0449.html has a lot of good points about the <canvas> element which we probably should integrate here.