The ASP.NET MVC framework is out and I'm sure people will be messing around with it. I'm still not sure how much AJAX is possible right now with this so we should see some samples hopefully (I'm trying to build one right now but not getting very far).
If this is all new to you and you're trying to get your head around the framework, here are the links to Scott Guthrie's mini-series on this epic.
Recommended Required reading to get used to the framework and now that it's out you can build the samples yourself.
There are more entries coming from the big guy, including information about the HtmlHelpers and AjaxHelpers (and how to build your own) but this will get you off the ground and flying in no time.
If you missed the link, you can grab the framework here.