PureMVC is quite a versatile MVC kit.  With implementations for AS3, .NET (c#), Python, PHP, Silverlight and other platforms it is quite a system and domain to spread that far and have consistency.  There are small changes but for the most post the MVC is the same structure across the platforms.  This can be very beneficial for a service firm or for a product base that needs to support many different platforms.

PureMVC is a lightweight framework  for creating applications based
upon the classic Model-View-Controller design meta-pattern.
This free, open-source framework is implemented in ActionScript 2 and
3, Java, C# and a number of other popular programming languages.
This allows development on a wide variety of platforms including:

• Mobile Environments: FlashLite, .NET Compact Framework, J2ME
• Server Environments: ColdFusion, J2EE, PHP, Python
• Browser Environments: Flash/Flex, JavaFX, Silverlight
• Desktop Environments: .NET, AIR, FLASH, J2SE

For Flex PureMVC happens to be my favorite MVC kit.  I only use one if absolutely necessary but PureMVC keeps it clean.  The great thing is that is works with or without Flex unlike Cairngorm and it is always up to date.  It is just an added bonus that is spans so many other platforms. There are a few things I don’t like about it in other platforms like the url naming but it is much better than kits out there now and Microsoft’s ASP.NET MVC most likely wont’ be cross platform *wink*.

Some info on the PureMVC framework (caution PDF):

• Goals & Benefits
• Conceptual Diagram
• Framework Overview
• Best Practices

PureMVC Manifold

• Documentation
• Project Owners
• Repositories
• Get Involved!

Ports

• ActionScript 2
• ActionScript 3
• C#
• ColdFusion
• Java
• Perl
• PHP
• Python
• Ruby
• Propose a Port

Mono is a great open source .NET implementation that has been looking to being a baseplane dream to .net development. They even have Moonlight which will eventually be caught up with Silverlight development.

However today mono gets a killer IDE in the MonoDevelop name.

[insertname]Develop projects are largely based on the SharpDevelop IDE that is one of my favorites with .net and is open source. If you are looking for a FAST IDE SharpDevelop is that. In the FAQ Miguel mentions that MonoDevelop is a port or branch of SharpDevelop which is great news for quality, speed and usability.

FlashDevelop is also another great kit based on this IDE framework. I am very pleased Mono is using the same standard for IDEs that mimic VS.NET only much more speedy and usable in SharpDevelop and FlashDevelop (both .net apps themselves and two of the only good winforms apps there ever were).

I highly recommend mono and MonoDevelop. These are tools that are baseplane languages and platforms that have all the benefits of .net development but for any platform and now for any platform as an IDE. One problem with FlashDevelop is that it is only for Windows machines but maybe MonoDevelop will influence and will allow it for other platforms as well and everyone will be able to use the best IDE there is for flash and flex development.

In the meantime if you are a .net developer and want to develop for multiple platforms not just Windows then Mono is your tool and MonoDevelop is your IDE.

The main features of MonoDevelop are:

• Customizable workbench, including custom key bindings, custom layouts, and external tools.
• Support for several languages, with C#, VB.NET and C/C++ support included, and Boo and Java (IKVM) support available as separate add-ins.
• Support for code completion and type information tooltips.
• Refactoring operations to simplify changes like renaming types and type members, encapsulating fields, overriding methods, or implementing interfaces.
• Code navigation operations such as jumping to variable definitions and finding derived classes.
• Easy to use GUI designer for GTK# applications, also supporting the creation and management of custom GTK# widget libraries.
• Integrated source code version control, with support for Subversion.
• Integrated unit testing based on NUnit.
• Support for ASP.NET projects, allowing web projects can be built and tested on XSP.
• Integrated database explorer and editor (beta).
• Integration with Monodoc, to provide documentation about classes.
• Support for makefiles, both generation and synchronization.
• Support for Microsoft Visual Studio project formats.
• Packaging system that allows generating tarballs, source code and binary packages.
• Command line tools for building and managing projects.
• Support for localization projects.
• Extensible add-in architecture.