A couple of Ajax features I've been thinking of developing:
- Saving forms with XMLHttpRequest: just display a success message at the top, and switch the "Cancel" button to "Done". Since the form's content doesn't change, this seems like a reasonable use of the technology.
- Switching out entire "content" <div> elements. Most of my apps have a <div id="content">, so it'd probably pretty easy to just replace that in response to button and link clicks. Of course, the hard part is having the requested server-side object load the view template, process it, and send back the content. This is probably more trouble than it's worth.