How can I implement a search field like this forums search field?

Is there a plugin that will give me the ability to implement a search field the same as this forums search field?

I’ve never used it, and don’t know how it might compare to the search field here, but here’s the most common search plugin. My guess would be that you will need to wrap the functionality from this in your own Ajax method in order to get a drop-down of results, if that’s the sort of thing you’re looking for.

The thing about the documentation here is that its not exactly clear on how to use it. I am following it word for word, but some parts are simply assumed that you know certain aspects of this model of searching (PRG). I myself have yet to get this work, although I have only been working with it for two days.