Disk w/ Flashing Question Mark, PLEASE RESPOND AS SOON AS POSSIBLE!

[the_crazy_one]

I was using MacOS X on my PowerBook. I put it to sleep and unplugged it (with the battery still inside). When I wanted to use it again, I noticed that the little LED wasn't blinking on the outside of the case. I pressed the power button and was greeted by the notorious disk with a flashing question mark icon.

Please respond as SOON AS POSSIBLE, because i REALLY need to use my computer, and I currently don't have access to any OS CDs. HELP!