I'm surprised it took this long for someone to release something like this, actually. Movement is a much-needed app from Jeff Stieler which reads your SpringBoard icon placement from your [jailbroken] iPhone or iPod Touch, and allows you to manipulate it and write back a new arrangement.
The app requires your device to be plugged in, and requires OS X 10.5 or higher (works on PPC as well as Intel). I had a few issues with getting the software to operate smoothly (icons kept disappearing when side scrolling in the app, and then reappearing if I let it sit), but it is a beta, and overall works well and is a solid idea.
I'm looking forward to seeing this one improved on. Its been muttered iTunes should have a built-in app organizer, with a few minor rumblings of rumored features, but nothing concrete. Movement to the rescue!