Boot your Mac in target mode and treat it like just another FireWire drive.
I got my brand-spanking-new 800MHz iBook the other day. I was short on time ? finishing this book, in fact ? but couldn't wait to make the switch from my existing Mac to my sleek, snappy bundle of OS X joy. How could I move all of my applications and home directory (/Users/rael)? I could do without the eternity I'd have to wait transferring it over the network. I didn't relish the number of CDs I'd have to burn to bring across all 3 gigabytes. And the idea of picking through the clutter on my external FireWire drive to make room left me ill.
If only I could mount my old machine's hard drive alongside the new one without tools and duct tape. Surely I could just treat my old Mac as a hard drive somehow. I sure could, and did.
It turns out you can mount one Mac's hard drive onto another Mac over FireWire quite easily. You simply tie them together with a FireWire cable and reboot one of them with the T (for target) key held down.
After just a few seconds, my old machine booted into what's known as target mode, the screen blinking a FireWire logo where usually there'd be a Mac OS X login screen. A click, spinup, and whirr later, my old hard drive showed up right on my new Mac's desktop.
Thanks to Macintosh's tradition of not spreading installed software all over the hard drive, I was able to drag over individual applications from my Applications folder. I dragged my home directory over and logged out and back in again and I was moved in, preferences and Desktop as I'd left them on the other machine. And all that in around 23 minutes, from boot to enjoy.
When you're done, eject the mounted drive by dragging it to the Trash or selecting it and pressing -E. As far as the target machine's concerned, just turn it off or reboot it when you're finished; it'll come back up as if it were all just a dream.