HP also claims to sell laptops with FreeDOS pre-installed (instead of Windows), but they seem to be impossible to acquire if (a) you're not in the US or (b) you're not a so-called Large Enterprise customer. And even then it seems to be quite hard. (I went to HP's US website pretending to be a Large Enterprise customer, but after filling in forms describing what sort of configuration I wanted, I was fobbed off with an nx6110 with Windows pre-installed.)
Novatech will at least sell you a system (desktop or laptop) with no OS at all on it, although they don't offer any support for Linux as such. I've got SuSE 9.2 running quite happily on a laptop I bought from them a couple of years back (although 8.2 didn't like the ProSavage graphics chipset).