GTK+ is a highly usable, feature rich toolkit for creating graphical user interfaces which boasts cross platform compatibility and an easy to use API. GTK+ it is written in C, but has bindings to many other popular programming languages such as C+, Python, Perl and C# among others. GTK is licensed under the GNU LGPL 2.1 allowing development of both free and proprietary software with GTK+ without any license fees or royalties. See GTK for more information.

An IDE for a number of scripting and markup languages. Newly open-sourced and based upon ActiveState’s well-established IDE and code base.

A set of modules for Python web development. Download page

Pyxer is a Python AJAX Server/ Framework similar to the Jaxer project of Aptana. Instead of writing client side code in Javascript you can use Python. The Python code will be translated to Javascript before send to the client. You may also have server side code defined in the HTML file that can asynchronously be called form the client with seamless use of AJAX in the background.