Mounting a CD/DVD's in 2013 seems like history (there's only one Mac still shipped with the SuperDrive: MacBook Pro), but you still do it from time to time. How frustrating it is, when this one time, disk doesn't show on desktop and yet it isn't ejected. Fortunately there's a way to manually mount CD/DVD using terminal. If you want to use it in OS X Lion and newer, use this:

$ mkdir /Volumes/pccd
$ /System/Library/Filesystems/cd9660.fs/Contents/Resources/cd9660.util -M disk1s0 /Volumes/pccd
$ disktool -r