I have used Memorex, Fellows, and Maxell brands and I think that Sharpies now makes a CD marker. My preference is the Maxell, though I could not give a scientific reason why.   They are harder to find whre I live. Some sound archivists on the ARSCList warn against writing on CDs or suggest marking on the inner clear part of the CD where no recording takes place.    The medium is still too recent to know what damage can be caused by markers. I usually write on the outer edge of the CD which is most often blank since CD writers work from the center out to the edge. There is some fear that the ink will bleed through to the recorded side of the CD and would interfere with the laser reading the contents of the CD. Epson makes relatively inexpensive printers that print to CDs, but they do use ink.   I