Dfyjkt

If you define a shadow ONCE, then it applies to all "graphics" on the canvas from thereon after (which is what it's supposed to do).

Sample:
http://flanvas.com/development/flanvas/test.html

Does anyone know best practice to turn the shadow off after you've used it? I'm setting shadowColor to "rgba(0,0,0,0)" which is a no-alpha black. I'm sure there is a better way.

case sample: The text is also getting a shadow. I'm using the no-alpha black to combat this for now.
http://flanvas.com/development/flanvas/examples/filters-dropShadowFilter.html

By using save, translate and restore you can perform your tasks without worrying about the style changes, for eg.

ctx.save();
ctx.translate(X,Y);

ctx.shadowColor = 'rgba(255, 0, 0, 0.5)';

// do some stuff

ctx.restore();

here X & Y are the co-ordinates where you intended to draw and you do your stuff relative to the co-ordinates 0,0.

This method solves the problem of caching and restoring the previous styles/values and is also very helpful when you work with gradients as they are always plotted relative to the origin (0,0)

(EDIT: Oops! I see that's what you were already doing with a 0 alpha black.)

This is what you were looking for:

context.shadowColor = "transparent";

It's usually a good idea to store the old value of these kind of "global" attributes before you change it and use this stored value to restore it later on. Example:

var origShadowColor = ctx.shadowColor;
ctx.shadowColor = 'rgba(255, 0, 0, 0.5)';

// ... do some stuff

ctx.shadowColor = origShadowColor;