You've probably heard already, but ASP.NET MVC has finally been officially released.
If, like me, you never really got on with the vanilla ASP.NET pipeline, then ASP.NET MVC offers a very different and understandable experience. The fact that you control the HTML a lot more closely also makes it ideal for jQuery and similar tools.
Add to that the testability built in, the ease of attaching IoC containers, and the simplicity of working with routes instead of pages, and you are onto a winner, IMO.
So if you want to use MVC-style web, with jQuery richness, and the power of the .NET framework behind you, give it a look.
For serious usage, I also recommend: