Here is how I went about creating a data DVD that is readable by both a Mac (OS X) and PC. First, install cdrtools. I did this by installing fink. Once that's done, then open a Terminal and type fink install cdrtools. Second, use mkisofs to create an image to burn. The command I used went something like this:
% mkisofs -J -r -o myimage.iso data_dirmyimage.iso is the name of the image file created, data_dir is the directory containing the stuff you want on the disc. After this command completes (how long it takes depends on how much stuff is in data_dir), use Disk Copy to burn the image to DVD.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20030323150105346