I'm a HUGE fan of jQuery. In fact in my latest project, I've removed the ScriptManager from my ASP.NET pages entirely. Originally I was including both jQuery and the ScriptManager on my pages because I just couldn't live without the ease and simplicity of calling page methods with ASP.NET AJAX.
Well, with a little help from Dave Ward and Rick Strahl, I realized that calling ASP.NET page methods (and web services) from jQuery is really pretty simple. More...