Did something unusual happen the last time you were using your computer? That might help diagnose your problem. If you can't even boot from a CD, your options for home remedy are limited.
Make sure when you boot from a CD you are pressing and holding the "c" key as soon as you hear the "BONG" tone on startup. Give it some time- booting from a CD can take a little while. If you can boot, run Apple Hardware Test and see where you stand. If your hardware is good, you can run disk utility to fix any HD issues.
Or, you could have a bad RAM module. If you have 2, try removing one and re-attempt startup. Make sure the remaining one is installed in the correct slot (read or download the user's guide for more info) Then if it doesn't work, switch them. It's unlikely that both went bad at the same time unless your computer was hit by a power surge or got wet.
Finally it's a long shot, but you can try resetting the SMC. The procedures are different for computers with removable batteries:
IF YOUR MACBOOK HAS A REMOVABLE BATTERY:
1. Shut down the computer.
2. Disconnect the MagSafe power adapter from the computer, if it's connected.
3. Remove the battery.
4. Press and hold the power button for 5 seconds.
5. Release the power button.
6. Reconnect the battery and MagSafe power adapter.
7. Press the power button to turn on the computer.
IF YOUR BATTERY IS NOT REMOVABLE (Early 2009 MBP or later):
1. Shut down the computer.
2. Plug in the MagSafe power adapter to a power source, connecting it to the Mac if its not already connected.
3. On the built-in keyboard, press the (left side) Shift-Control-Option keys and the power button at the same time.
4. Release all the keys and the power button at the same time.
5. Press the power button to turn on the computer.
Note: The LED on the MagSafe power adapter may change states or temporarily turn off when you reset the SMC.
If that doesn't work, this is where I'd take my computer to a certified Mac repair location.