jQuery SVG is a nice structured plugin that allows you to interact with SVG-Canvas Elements. It also features extensions for graphing and plotting.
Raphaël on the other hand is a simply kept library to handle your Vector-Graphics needs on the web. Especially interesting is the support of SVG as well as VML. The last one providing a decent fallback for some well known not-so-good browsers.
Interesting new development: mozilla added mozRequestAnimationFrame for better animation timing with html5 / css3 browsers. Looks very interesting, the only drawback is, that it is an experiment and not guaranteed to stay.