I have heard of people having success using something thin (like a strip of plastic) with a something sticky on the end to pull it back out. Maybe a long strip of scotch tape securely attached to the plastic, and then wrapped around with the sticky side out?
The problem being, that you don't want to lose the sticky part back in the drive, and you don't want to poke around too much in there. Although I suppose it doesn't work anyway.
Long thin tweezers might work too. I used some to get TWO cd's that were inserted at the same time (aren't kids great!)...
Have you tried holding the Macbook with the slot down (lid closed), and gently shaking it to see if you can at least move it towards the front of the slot? If you can get it close enough, you should be able to use regular tweezers.
You might also want to try taking it into an Apple store if one is close by. They might be able to help.
If you absolutely can't get it out, and it is not under warranty, You may be able to get a replacement drive, although I couldn't find any with a quick google search...
You can always use an external CD/DVD USB or firewire drive...