Viruses today could send it selfs all over internet via your outlook contact list or MSN or spread using IRC or attack Microsoft web servers, etc. All of this is really annoying but a real pain is to loose information, word documents thrashed or operating system files deleted. I'm going beyond this talking about Hardware Damage.
I'm not writing this for the joy of virus writers, if so it's for hardware vendors and driver writers who could really take hands on that.
Guessing possible attacks we could prevent them easily.

Not so easily, this is not a new idea, do you remember CIH aka Chenobyl virus? This one depending on the virus version, checks for system date and if it's April 6th it deletes your hard disk info and writes your motherboard BIOS with chunk data.
What does it mean? Apart from loosing all your personal files and operating system, you couldn't boot that computer again until this bios chip is rewritten.
This is not a real "hardware damage" because flashing again the bios it will work again.

New viruses that have to come will be very smart as virus writers are. What kind of hardware attacks must be aware of?
Bios are well knows because of CIH viruses and now most motherboards have a jumper on the mainboard or a option on BIOS setup to disable BIOS chip writting.

This are a few attacks that I found possible:

Unspected CD-ROM burning.

Imagine your private files stored on a CD and that CD is inside the CD drive, a virus could began a burning process to damage your multisesion or write erratic data on the support.

Monitor Resolution changing.

You left the computer some minutes to have a coffee and while you are away a deathly screensaver becomes active. I will change then resolution of your monitor and the Hhz frequency as well. Changing from 640x480 to 1280x1024 multiple times in a second. A process like that running several minutes could really kill your monitor.

CD-ROM ejecting loop.

The same philosophy as the monitor resolution changing but ejecting and inserting the CD tray, not so deathly but disgusting.

Consuming all your ink.

The virus could send commands to your printer to clean the print cartridges and waisting off your expensive ink.

Far beyond damaging files or even hardware, there are the user. If viruses could damage your hardware, could them damage you?
The answer is: Not directly but, the virus could alter hardware normal behavior to make it "dangerous" for the user health.
This are a few examples:

Monitor flicking.

You are working as usual with your computer and a little flickering apears on the screen, but not even a second. Repeat this operation for some minutes and indeed it will disturb you.
Another annoyance is that whatever resolution you choose, when you go away and the screensaver goes on, the monitor frequency is set to something like 50Hz or 60Hz, looking many hours to a screen being set to that resolution could cause eye damage on the future.

Speaker low frequency sounds.

An annoying beeeeeeeeeeeeep at a very low frequency played sometimes and during long time periods could streess you a lot.

Mouse not responding.

A virus that disobeis mouse orders and even cleaning the mouse ball it doesn't work will make you to do not perform your work in  an efficient way

Eject CDROMs at top-speed spinning?

I can say I experienced this fenomenon, opening the CD tray the CD don't spin down and it fly itself rigth to my neck spinning like hell. I didn't get hurt but it could really scary you, believe me! I thougth this can not be acomplished by a virus because is a hardware mechanism, but maybe I'm wrong.