It is becoming increasingly rare, still from time to time I get a DVD or CDROM as installation media. To create an iso-image from optical media under Ubuntu, run:

readom dev=device -f file.iso
# e.g.:
readom dev=/dev/disk/by-label/your-media-label -f /place/to/store/the/image.iso

The program readom (read optical media) a is available from the package wodim

apt-get install wodim

readom serves for me better than dd as it has build-in error checking and shows progress out-of-the-box.