I know how to mount a drive that has a corresponding device file in /dev, but I don't know how to do this for a disk image that does not represent a physical device and does not have an analogue in /dev (e.g. an ISO file or a floppy image).  I know I can do this in Mac OS X by double-clicking on the disk image's icon in Finder, which will mount the drive automatically, but I would like to be able to do this from the terminal.  I'm not sure if there is a general Unix way of doing this, or if this is platform-specific.
How to mount a disk image from the command line?
mount;disk image