As most know putting labels on a CD or DVD can be problematic with certain types of hardware, especially a car CD player. The player may either not read the disk or the disk gets stuck in the player because of the label. I just bought the new Casio CD-R, DVD-R Disc title printer, and although I have not been much of a Casio fan, I believe the idea behind it is great. It prints the information right onto the disc so no paper label getting stuck. I hope to see other models hit the market that may be a little more advance than this one. The current Unit CW-75 runs on batteries (8 AA), or if you purchase the adapter than from power. It can be used either with your computer with the software loaded or stand alone. Currently it can only take one printer ribbon at a time, and I would like to see this changes so more colors can be added to the text you will put on the disc. All in all not a bad first attempt. The unit sells for $99 with a twenty dollar rebate until March 2006.
Good point but if you are doing something you want to look professional than something more than a marking pen may be needed.
If labels are necessary, just make sure your labelling device can center that label to near perfection...otherwise it's a coaster, and can damage CD drives due to imbalance. For me, heh, Sharpie has my vote. If I really wanted to get into labelling my disks though, I'd go the route of printing the surface of the disk directly from a printer, or use LightScribe.