Also known as a USB key, USB hard drive, USB keychain hard drive or USB diskette, this refers to a solid state storage unit coupled to a male USB connector on a device the size of a keychain.

While portable solid state memory is not a new technology (e.g. Sony's Memory Stick, CompactFlash, SmartMedia, etc.), most solid state memory modules are of a proprietary nature -- usually directly coupled to a particular brand of digital camera, and almost always requiring special hardware in order to interface with a PC.

However, USB keychains combine the stability and convieneince of solid state memory (no moving parts == Good Thing) with the ease and ubiquity of the non-propietary USB interface. Ultimately this technology may finally succeed where zip disks have fallen short: that is, replacing floppy disks as the common pluri-compatible method of data transfer between PC's.

At the time of this write-up, the following USB keychain products are available in capacities ranging from 8 to 128MB (including the powers of two in-between):

Personally, they are a bit pricey at this time, but when the price comes down I'll get myself a nice USB hub and a few of these. And if anybody figures out how to boot off of one of these babies, I don't think I'll ever own a FDD again . . .

Update! 3 Feb 2002: generic-man kindly informs me that "some BIOSes can boot to USB right now. I've heard tales of people using USB keys to do minimal Debian installs."