News.com have a neat gallery of pictures showing the evolution of the hard drive.
The gallery has pictures ranging from the first hard drive, a 24″, 50 platter monster, which had a capacity of, wait for it, … 5MB, through the first mainframe harddrive that a single human could carry (in 1982), to 1″ microdrives from Hitachi. Interestingly, the 1″ microdrive appeared in 1999 but did not find a mass market until the iPod Mini just last year.