ASP.NET released an implementation of the MVC (Model-View-Controller) design pattern recently. A good introduction to the MVC pattern in general and to the ASP.NET's implementation of it can be found on Scott Gutherie's blog.
Our very own Jon Smith ("pilgrim"), who a lot of our customers probably think of as a god-send because he leads our customer experience initiatives has blogged on using ActiveReports Web Viewer with the ASP.NET MVC 1.0.
As he explains..."The ActiveReports WebViewer was designed for ASP.NET WebForms, not for ViewPages in MVC. Therefore we still need a little bit of code-behind for the WebViewer to work. This can be accomplished by adding a WebForm to the Views folder and changing the code-behind class to inherit off of System.Web.Mvc.ViewPage instead System.Web.UI.Page."
Read more and view his screencast on his blog.
Billy McCafferty (twitter.com/devlicious) has written a great post on integrating ASP.NET MVC with ActiveReports for .NET on his blog.