There are also Fab.js http://github.com/jed/fab (which hasn't seen any updates in a while, but I'm sure it's still being worked on), Pintura http://github.com/kriszyp/pintura and Picard http://github.com/dantebronto/picard

At a lower level of abstractions are the middleware layers Connect http://github.com/extjs/Connect and JSGI http://github.com/kriszyp/jsgi-node