The technologies comprising AJAX have been around for several years, but their inherent complexity forestalled widespread adoption. AJAX frameworks are designed to make AJAX development easier. It is these frameworks that enable the whole Web 2.0 motion (and corresponding hype).
Atlas is Microsoft's AJAX framework, based on ASP.NET 2.0. It comes with server-side controls that encapsulate the client-side functionality. Most useful is the UpdatePanel control, that allows the developer to convert any events raised from traditional ASP.NET server controls from full page postbacks into flicker-free AJAX-style partial page updating.
Bertrand LeRoy and Matt Gibs who are working on the UpdatePanel control at Microsoft have written an O'Reilly shortcut "Atlas UpdatePanel Control" that shows you how to apply the UpdatePanel. After some introductory explanations they show three well-chosen real-world examples, that are so close to common ASP.NET pages that you immediately understand how to apply the UpdatePanel in your own websites. The examples also include many tips and best practices on other aspects of ASP.NET and Atlas programming, with references for further study.
Shortcuts are short introductions to a brandnew topic that you can download as a PDF file. Until a book with a complete coverage of the Atlas framework and corresponding control toolkit comes along, this one shows you all you need to know to get going with the update panel, and is highly recommended.