JsHttpRequest is a powerful library to create AJAX-based websites in PHP. It could be used as a PHP part for Prototype JS. Great cross-browser compatibility (works even without XMLHttpRequest!), national encodings support, AJAX-style file uploading.
Ajax-Controls.NET component is designed to provide developers with an easy-to-use tool to AJAX enable standard ASP.NET controls and 3rd party controls in ASP.NET application, which allow you to update page content without postback and loss of scroll