What's the iPhone application called that allows you to scroll through your home screen?

Dock.

Are you talking about having multiple Home screens? You can do that without jailbreaking.

http://en.wikipedia.org/wiki/Springboard_(iPhone)

?

On second thought, don’t use dock. It is what you are asking about, but it’s a nuisance. It just gets in the way when you are trying to do things.

@pup & jp, he’s talking about a jailbreak app that let’s you scroll through the apps individually rather than through the homescreens.

once you add more icons, more than the main screen can handle, a new page will form and you will be able to scroll back and forth between pages. And it can handle more than two. Pages will be indicated by small white dots on the bottom of the screen.

That isn’t what I’m talking about. I’m talking about scrolling up and down on the home page.

Yes, that used to be done with Summerboard. After about 1.1.3 though the capability was built in by Apple, although it scrolls horizontally, not vertically.