Diamond Multimedia Rio PMP300 (1998)

The Nano it ain't, but Diamond's Multimedia Rio PMP 300 started the revolution that produced portable music players such as Apple's iPod (#2). This first portable MP3 player ran on a single AA battery and packed a whopping 32MB of storage--enough for about a half hour of music encoded in the MP3 compression format. Read PC World's original review. Photo courtesy of The Adrenaline Vault.