In the event of a blank,corrupted, or otherwise failed BIOS:
1. Visit the website of your board manufacturer.
2. Download the latest BIOS.
3. Put the BIOS on a floppy.
4. Insert the floppy and reboot.

I would never suggest hotflashing your BIOS. Unless you're very lucky, both motherboards will die.
Some nifty motherboards come with dual BIOS to protect against catastrophic failure.

Where to get BIOS updates (depends on who made your board):

Abit - http://www.abit-usa.com/
AsusTek - http://www.asus.com/
GigaByte - http://www.giga-byte.com/
Tyan - http://www.tyan.com/

If your machine's hosed even beyond that, you can boot up another, working motherboard (preferably of the same model, and at least using the same flash util and chip size), prise out its bios chip (yes, while it's running), put in the hosed one, and run the bios flash. Done incorrectly, this is a great way to hose two motherboards.

If you know someone with an EEPROM blower, use that instead. It's much safer.

Finally, if the flash program exits to dos, Don't switch off or reboot. Run it again while you still can (Especially if it's a laptop... Break them and it's a return to base job...)