Lily is an Open Source, browser-based, visual programming environment written in JavaScript. Lily enables users to build programs graphically by connecting functional modules to fetch and direct the flow of data, play sound or video, add interactivity or display results. Lily programs can be shared with other Lily users, installed as Firefox add-ons, run as standalone apps using XULrunner, or (with some limitations) be embedded in a web page.

There are over 150 modules available: web service modules for apis like Amazon, Flickr, Wikipedia, Yahoo, etc; UI modules that wrap widgets from YUI, Scriptaculous, JQuery, Google Maps, etc as well as the browser's built-in UI elements; modules that offer privileged access to SQLite storage, sockets or the file system; graphics modules that encapsulate SVG and Canvas functionality and multimedia modules for playing sound and video. Modules are written in JavaScript (like Lily itself) and it's dead simple to write a module to do pretty much whatever you want.

For more information have a look at the project homepage: http://www.lilyapp.org