While there has recently been an increase in the buzz regarding frameworks, design patterns, and MVC architectures, they really are not new concepts. In fact, the MVC design pattern has probably been around longer than a number of the people actively reading this blog.
The MVC (Model-View-Controller) architecture was conceived by Trygve Reenskaug at Xerox PARC in 1979 while working with SmallTalk. MVC originated in desktop applications, and relatively recently made its way into web based applications. Many modern RIA frameworks closely resemble the older desktop client-server architecture, and the resurgence of MVC popularity makes sense.
I found these links to be particularly interesting on the topic of MVC, and they are in the words of the original MVC creator himself:
MVC XEROX PARC 1978-79
A description of MVC and its origins.
MODELS - VIEWS - CONTROLLERS
A great description of the logical components of MVC.
The Model-View-Controller (MVC) Its Past and Present
More detail about the MVC pattern and its evolution.
You can learn more about MVC, and its application to various technologies at: http://en.wikipedia.org/wiki/Model-view-controller
The concepts introduced by the model-view controller pattern are the driving factors for all major Flex frameworks, including: