http://docs.info.apple.com/article.html?artnum=88275
(I used the link I gave you for powerbook instructions and when it loaded I typed into the search window "mac book ejecting a disk". I hope this helps and you find the advise instructive. Metaphorically speaking, I'm trying to teach you how to fish as well as trying to solve your problem)
The above link takes you to your model and trouble shooting the load slot on the disk drive. Opem it and Take a look at it. There doesn't seem to be a magic wand just methodically follow the instructions.
Bellow is part of that link and will give you key combinations and instructions.. I have a MB Pro I'm glad I 've never run into this problem. It looks like all of the options involve shutting down and restarting with exception of the F12 key. Resetting your PRAM requires starting and holding down 4 keys, Command, Option, P, R simultaenously before you get a start up chime.
The drive doesn't eject discs
If the drive ejects discs slowly or appears to be struggling, insert and eject a disc several times.
If the drive does not eject discs,
press the F12 key or, on original PowerBook G4 computers, the manual eject button located on the side of the slot.
Holding down the trackpad button during startup should also eject a disc.
Reset the parameter RAM (PRAM) and/or the Power Manager (PMU). PMU reset instructions for iBook G4/PowerBook G4 or for MacBook/MacBook Pro (both 15-inch and 17-inch models). (there is a link to instructions for both of these operations in the link at the top of the page. Do PRAM first the other one, PMU, should be your last choice before taking it in to a technician.)
If the disc still does not eject, contact Apple to arrange for service.
(Gulp, do you have extended care or is it less than a year old? If so calling apple or taking it to a tech or an Apple store won't be as unpleasant.) You may be stuck with a repair. The above linked article specifcally mentions CD sizes and shapes.
I'm reluctant to mention it but, Ok, here goes da bomb. Are you handy with tools and do you trust yourself to take apart the computer to get at the optical drive? I'm not sure if this your model but
powerbookmedic is a great resource.
Don't do it if you don't think you have the skill. There is nothing like the experience of turning your own computer into an expensive paper weight.
http://www.powerbookmedic.com/Manuals/13-inch-macbook-manual.pdf
If nothing else this may give you a better understanding of your machine.