Apple won't sell you a 500GB hard disk for your Mac yet, but Seagate will. We've been testing Seagate's 2.5-inch Momentus 5400.6 500GB ST9500325AS SATA hard disk, which works a treat in the new unibody MacBooks, and is compatible with PlayStation 3 consoles.
500GB is a whole hell of a lot of storage, and 180GB more than the maximum drive capacity of 320GB that Apple sells. And, this much larger drive will only cost you about £75.
Once installed and formatted, you'll get about 460GB of usable space. It's a quiet little 5400RPM disk like the ones that come with new MacBooks, giving maximum read speeds inside our Mac of 67.04MB/s and write speeds of 66.91MB/s. We tested with a 2008 Unibody MacBook with 2GB of RAM and a 2.0GHz Intel Core 2 Duo CPU, using Xbench.
Replacing a hard disk is not difficult -- and in the new Unibody MacBooks, fitting your own doesn't invalidate your warranty -- but we still don't advise you attempt it unless you're certain you know what you're fiddling with. But it took us a couple of minutes to get the disk fitted, and very chuffed we are with it too. It's fast enough for most laptop functions, quiet, and a stonking upgrade option for media hoarders.