Don’t know if this tools can be useful to create browser games.. I added this programs to the Gamemaker archive section anyway..
Ruby on rails is an open-source web framework that includes everything needed to create database-backed web applications according to the Model-View-Control pattern.
Available for windows, macintosh and probably linux (source).
Prototype is a JavaScript Framework that aims to ease development of dynamic web applications.
Featuring a unique, easy-to-use toolkit for class-driven development and the nicest Ajax library around, Prototype is quickly becoming the codebase of choice for web application developers everywhere.
jQuery is a fast and concise JavaScript Library that simplifies HTML document traversing, event handling, animating, and Ajax interactions for rapid web development. jQuery is designed to change the way that you write JavaScript.
and last but not least…
A nice and free IDE for PHP/HTML/CSS/JavaScript development.
