Home-Buildable Laptops?

So is it at all possible to buy a case, mobo, processor, graphics card, HDD, RAM, all that other jazz and build a laptop? 

It'll probably be more costly than buying a laptop with what I need (Built-in Atheros wireless-G and Bluetooth, a decent GPU, 2.8+ ghz P4 or 2.0 ghz Centrino, 1gb DDR) but I was just curious to see if it was doable or if someone's done it before. 

I don't think you really can.

No it's not, any more than you can build an iMac. They're designed as integrated units rather than a set of hardware modules which is all a PC is.

The closest you could get home-built would be to make some sort of custom mini-ITX case with an integrated keyboard and an LCD monitor on a hinge, but it still wouldn't be battery powered (unless you add a socking great battery, and even then the components are not designed for low power consumption). It wouldn't exactly be tiny though - the slimmest mini-ITX case I know of is still two inches deep, and unless you cannibalised an LCD panel from a dead laptop, regular LCD displays are a bit on the chunky size too. You'd end up with a kind of vast, clunky, cobbled-together, barely-usable ugly monstrosity that cost more to make than buying an actual laptop. Stupid, stupid, stupid.

You can custom build a laptop, but your choice of parts for each chassis is severely limited, and you'd have a mess of wiring and Frankensteinian garbage hanging out if the LCD and bezel you chose  weren't made for the lower end.

It's possible, just really, really expensive and altogether pointless.