Whispers,
You and I, my friend, have been constantly searching for this solution. I know EXACTLY what you want. You want the site to load even when it's idle (e.g. when someone is reading content on the homepage), that way when they click a link, they "finish" or bypass the preload process. I've read the tutorials that monsterfx posted and they get right to the heart of the matter.

I will now bounce ideas off you for feedback and maybe together we can get somewhere with this thing! Here's what I'm seeing....

Say we have a main timeline that loads in two separate swfs (a small example of a site).

Each of the swfs will be loaded into its own level with a stop action on the first frame with no content which will make it invisible. The "loadMovie" action will do this for each of the swfs in the maintimeline. This, I guess, is the definition of "parking" a movie. I've read this is better than using "_visible", because that causes a loaded movie's contents to flicker when the button is pressed, so I've given up on that technique all together.

Lets say we initiate a loadMovie for each swf in the first frame of the main timeline with each loadmovie command in a separate layer. I don't think you can have TWO loadMovie commands in one layer in the same frame (I could be wrong here)....

Now for my dilemma and more than likely one considered by Whipsers as well....

What if a person is done reading the homepage content and clicks a link while the loadMovie process is going on for the targeted swf?

I'm going to try to facilitate an example to explore a theory I have, but if anyone has anything to add, then cool!