SVG vs. Canvas: Tastes Great, or Less Filling?

Now that there are two up-and-coming web graphics technologies (SVG and canvas), I thought I'd research them,
see what's the difference between them, and see if they're usable now.

Canvas Tag

The canvas tag got a lot of attention a while back when Apple announced they were adding it to their Safari browser,
and that they were using it to implement some of their Dashboard widgets.
What is it? Basically, the canvas tag is an "immediate mode" graphics technology -- you start with an empty image jammed into your browser
page, and it's your job to color ...

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