Lightscribe lets you print grayscale images/text directly onto the surface of specially coated CDs and DVDs using the laser in your optical drive.
- high resolution images
- no need for special printer
- more expensive than inkjet printable media
- contrast is not great (I've read that printing multiple times can improve this, but not tried it myself)
- takes a long time (30 mins+ for best resolution)
- may reduce the lifetime of your laser
The software is available for free for Nero, and I guess for other software, but I've only ever used it with Nero.