There are tons of possibilities with AJAX, and most of them starts with the (simple) functions listed above...
There are a few challenges by using AJAX like cross-browser compatibility and browsers that doesn't support JavaScript or have it disabled.
So you may end up with several different versions of the JavaScript functions to support the major browsers, and It can also be a good idea to create a non-JavaScript (no AJAX) version of the site/page as well.
So larger "Ajaxified" sites can be a real challenge to produce and normally requires lots of more coding than traditional sites do...
But it's quite interesting, and I've only started to "scratch the surface" of AJAX now.
