Protovis is a JavaScript framework packed full of ready-to-use visualization components like bar and line graphs, force-directed layouts of networks, and other common building blocks. It’s great as a high-level interface to a toolkit of existing visualization templates, but compared to Processing, it’s not as easy to build completely new components. Its developers have recently announced that Protovis will no longer be under active development, as they focus their efforts on the D3 library, which offers similar functionality but in a style heavily influenced by the new generation of JavaScript frameworks like jQuery.
