http://callbackpage.softain.com/

CallbackPage is the easiest wary to include AJAX functionality in your web
sites. A project is developed as an usual ASP.NET application, using
standard VisualStudio and/or third-party components. All you need to
transform the site to an AJAX application is to define blocks to upload
after the users' acts and customize the templates. The result application
will look for any user as an usual web site - with correct behaviour of Back
and Forward buttons and static links. But the site won't be reloaded after
each request to the server. Only necessary part of a page will be updated.