This name has made boom in web application development.Every days it is getting more and more popular.Ajax is a not a new language or standard but it is a simply a technique to use existing standard and development technology in to better way for creating better,Faster and more interactive and reach user interface web applications like desktop application.
The Big Company like Google and Microsoft already moving towards that with Google Suggest,Google Earth and Microsoft's live.com and live mail beta.
AJAX and ASP.NET:
So, Microsoft has also provided a Ajax framework called "Atlas" to develop ajax enabled application with the Microsoft ASP.NET 2.0 plate form. It provides easy to develop Ajax functionlity with out writing such heavy java script and XML codes.You can make your existing application Ajax enabled within the few minutes with that framework.
For more details Please visit http://atlas.asp.net/