Vector graphics in Javascript?

I've used Raphaël Javascript Library and it worked quite well. Currently the library supports Firefox 3.0+, Safari 3.0+, Opera 9.5+ and Internet Explorer 6.0+.

Give a look to Cake, Processing.js and jQuery SVG Integration Plugin.

Also check the Canvas element reference.

I know this is a pretty old question, but in case anyone comes across this question, the most impressive vector graphics I've seen in JavaScript is Paper.js.

Hope that helps.