The Internet Communications Engine (Ice) is a modern object-oriented middleware with support for C++, .NET, Java, Python, Objective-C, Ruby, and PHP. Ice is used in many mission-critical projects by companies all over the world. Ice is easy to learn, yet provides a powerful network infrastructure and vast array of features for demanding technical applications. Ice is free software, available with full source, and released under the terms of GNU General Public License (GPL). Commercial licenses are available for customers who wish to use Ice for closed-source software.
Pinax is an open-source platform built on the Django Web Framework. By integrating numerous reusable Django apps to take care of the things that many sites have in common, it lets you focus on what makes your site different.
plasTeX is a LaTeX document processing framework written entirely in Python. It currently comes bundled with an XHTML renderer (including multiple themes), as well as a way to simply dump the document to a generic form of XML. Other renderers can be added as well and are planned for future releases.
Sage lets you build rich, highly functional, cross platform web-enabled desktop applications and applets by simply marking up the UI and attaching JavaScript (or Ruby, Python, etc.) event handlers. You simply point sage to a URL and it downloads the markup and accompanying scripts and renders the application or applet in real-time (the same way a browser renders documents). All that is required to run Sage is a Java Virtual Machine (v1.5 or later, v1.6 preferred).
Myghty is a Python based templating framework originally based on HTML::Mason, the enterprise-level framework used by Amazon.com, del.icio.us and Salon.com,
Sajax is an open source tool to make programming websites using the Ajax framework — also known as XMLHTTPRequest or remote scripting — as easy as possible. Sajax makes it easy to call PHP, Perl or Python functions from your webpages via JavaScript without performing a browser refresh. The toolkit does 99% of the work for you so you have no excuse to not use it.