Carl Backstrom has provided some truly amazing HTML DB AJAX & DHTML examples on his demo page on htmldb.oracle.com. Most of them are documented, but they assume that you have more of a technical background than not.
With Carl’s blessings, I took one of his examples – AJAX Process on Demand – and created a working example of an AJAX-based Select List. The example is quite simple: select an Employee Name, and the Job field will automatically be populated with the corresponding Job from the EMP table. This is a common behavior in Oracle Forms (when a user select one thing, another field is auto-populated) and will make the transition for those coming from a Forms environment a bit easier.