So, what can you do with an old PC notebook and some time on your hands? Why not try getting Mac OS X Leopard to run on it. Turned out not to be too difficult at all, if you look around you'll find detailed walkthroughs on how to get it done.
These are some specs of my old Acer TravelMate 8006 LMi notebook:
Intel Pentium M 755 2 GHz 512 MB DDR SDRAM ATI Mobility Radeon 9700 - 128 MB
As you'll see in the video above, it takes a little while for Leopard to boot but it does run pretty slick. Unfortunately my wifi card (Intel2200BG) was not supported out of the box so had to go with a third party port for Darwin which is not quite there yet making wifi connectivity a bit of a pain to set up.
You mileage may vary in getting it installed, what worked for me was formatting the partition as Master Boot Record using Disk Utility in the setup and then customizing the install, deselecting everything except for the EFI boot loader for MBR.
From there onwards the install is pretty straightforward, when you boot up again afterwards it appeared to be stuck on the Apple boot screen. That is in fact not the case, it for some reason takes an incredibly long time to get through it the first time you run -- probably close to 45 minutes.
Its an interesting proof of concept, nice to play around with but I think I'll end up installing something like Ubuntu after I've tested it some more -- unless of course Apple decides to officially support it (and pigs fly) ;)