This tool is the work of Dmytro Kryvko (DMK Software) - I haven't changed a thing in the extension intself. However, this extension was moved to .Net 4.5 and put into a Visual Studio Package file (.vsix) in order to give a better support for VS 2012.
This is the original description by the creator:
One of the great new features of the Visual Studio 2005/2008 .NET IDE is a custom tool called ResXFileCodeGenerator that is automatically associated with resources (*.resx files) every time they are added into a project. Whenever your project is rebuilt, a resource file is saved or a custom tool is run manually; the tool in question generates a managed class that exposes every resource you have in the *.resx file as a strongly typed static property. Now, any type of resource supported -- including images, icons, strings, etc. -- is a piece of cake to retrieve.
Original code and VS 2005/2008 install files can be found here.
Source code for this version can be found here.
Extension for Visual Studio 2005/2008 as was published by the creator can be foundhere.