I first heard about AJAX a while ago but never had the time to check it out properly but then i came across Michael Schwartz's AJAX Wrapper for .Net and hacked around with it for a while. It's incredibly simple to use, you simple add the HttpHandler to you web.config, add a custom attribute on the methods you want to expose sand add another custom attribute to the classes you want to transport and write a bit of JavaScript. The control I wrote was a simple category selector but by using this technique I'm able to remove allot of postbacks from my web application. PostBacks seems harmless enough but should be used sparingly in large projects - especially is the pages are large and ViewState is used heavily. I don't think I'm going to be ditching winforms just yet like but I'll certainly be using AJAX where possible.

You can download the dll from Michael's blog

http://weblogs.asp.net/mschwarz/archive/2005/04/07/397504.aspx