DotNetNuke (DNN) is the premier open-source Windows based  Web Application Framework.     Under the leadership of Shaun Walker, DNN has grown into one of the most successful open-source projects to-date.  It has proven itself as a Content Management System (CMS) as well as a Rapid Application Development (RAD) framework for web applications.    Its rapid adoption and acceptance can be traced to the following five things: Built-in Functionality Extensibility Stability Support Infrastructure Low Cost of Entry With its built-in functionality which includes things such as User Memberships and Profiles, Role based security,  Skinability, and a host of modular functionality which includes things like Blogs, HTML/Text, RSS, Links, Forums, Image Galleries, Mailing LIst subscriptions, Survey's, Feedback, and many many more, you might wonder why such effort was taken to make sure it is Extensible.  However, since almost all of the functionality of DNN is either provider based or modular, it is not surprising that new functionality is showing up in the market place every day as companies extend DNN to meet their needs. Starting with a framework of core functionality, such as is offered by DNN, leads to an extremely stable application.  However, as we are all aware, problems and changes in requirements do happen.  With the wide acceptance of DNN over the last 4 years, a huge Support Infrastructure has developed.  Skinners and Module Developers are readily available.  On top of that, the Core Team has made itself available for support through the DotNetNuke Corporation. Last but not least, the low cost of entry into the DNN world has helped fuel it's wildfire growth.  Since companies don't have to spend tens of thousands of dollars on licensing fees, they can use their resources in implementation to develop a professional web application that fits in with their business plans and needs. Hardy Consulting, Inc. (HCI) has been working with DNN since it's inception and release by Shaun in 2002 when it was known as IBuySpy Workshop.  Our first production sites utilizing DNN went live in early 2003.  We have found that DNN does not fit everyone's needs.  But, for those whose needs it does fit, DNN can save an immense amount of time, effort, and money as you do not have to re-invent the wheel nor spend resources on large licensing fees.