Gobby is a free collaborative editor based on libobby, a library which provides synced document buffers. It supports multiple documents in one session and a multi-user chat. It runs on Microsoft Windows, Mac OS X, Linux and other Unix-like platforms.
Chickenfoot is a tool that puts a programming environment in Firefox so you can write scripts to manipulate web pages and automate web browsing. In Chickenfoot, scripts are written in a superset of Javascript that includes special functions specific to we
Lily is a Firefox add-on that allows users to create rich, complex applications in a web browser. With Lily it's possible to make programs that mashup the web or the desktop, visualize and animate data, modify webpages, play music, or connect to world outside the computer.