An old topic of mine,but with a new slant. I have finally got a printer which will print from Windows and Linux.I am still using my Lexmark C730 series on my second PC(which doesnt have Linux anyway) but for my main PC,I got hold of a not quite new HP Officejet 5500 series all-in-one printer from my works stores.Drivers for this are already installed in Vista and they seem to be already installed in Linux too as I didnt download anything but I can print fine under both systems.So for me,Linux has passed it`s final test with flying colours.Of course there will be some apps which I want to use which will only work with one system or the other but that is not a problem anyway. Regards Kenny
Someone may have said this before, but, before you buy printers, it’s always worth checking them out on this site:
http://www.openprinting.org/printers
Though, most HP’s do work on both Linux out-of-the-box 
I agree, always check openprinting.org before buying a printer.
Other “general” rules of thumb are…
It’s pretty much hard to go wrong (although probably not impossible) with -
NVIDIA graphics cards (geforce4/5 onwaards)
HP Printers and All-In-Ones
and (IMO) Wireless cards based on an Atheros chipset (although it must be said, some may require compiling for WPA/2 support)
But as with buying hardware for Windows, do your homework first… you wouldn’t after all buy hardware for Windows without checking it supported your version 