first of all, did you have a look at this before posting:
here's what I experienced:
: ATI and nVidia are no prob as long as you install proprietary drivers (Ubuntu has ways to do that automatically of you have internet on that PC); I don't have experience using ATI cards; Intel cards are supported by standard Linux tools (X11 drivers), though I don't know if all of them (my onboard chip works out of the box)
: I never experienced an issue with HDD's, anything from floppies to some TB mobile drives should be fine (though you can't exactly install Ubuntu on a floppy
, USB drives can only boot if supported by the bios)
: same as HDD's, though sound cards and WLAN can be hairy (generally look at what chips are built-in, e.g. Intel sound should be working fine, but most others too)
: again, all I know that the hardware that I tried worked out of the box
: Now this can be hairy. For my WG311v3 chip on my NetLink card I need to use the windows drivers via ndiswrapper (a kernel module that uses windows "inf" files). But there are also a lot of wlan drivers in the linux kernel (my brother has a card that is supported by the kernel, I can only ask him next monday about that because he is away for a week)
Generally speaking, you don't
need special hardware for Linux, especially if you don't plan to game under Linux.
Have a lot of fun.