Ajax is one of most hot and upcoming technologies for web developement plateform. Microsoft has launched its ajax development kit . With it you can easily create ajax enabled application with asp.net . With help it takes few mintues to convert existing asp.net application to ajax enabled asp.net application.Microsoft also lauched some tutorial and video with it’s How do I ajax video series. It is 25 video which cover all aspects of ajax development.Any one can download it with following links.
http://www.asp.net/learn/videos/default.aspx?tabid=63