You know the devices; possibly the most well known is the Marvell plug computer line. Its flagship product, the SheevaPlug, offers a 1.2GHz ARM-compatible Marvell Sheeva processor, USB 2.0 and gigabit Ethernet, 512Mb Flash RAM and 512Mb DDR2 RAM.
Those specifications are not anything to write home about, particularly when you consider even the teeniest Netbook ships with 4Gb of flash memory.
This is where you have to actually see the device; check out the plug computer info sheet from Ionics EMS and you will see just why these gadgets are dubbed 'plug computers' and 'wall warts'. They literally are no bigger than a typical power brick for a powered USB hard drive or some phone chargers.
Yet, that's the whole computer - and that's where the appeal comes in. Well, that and the sub $US 100 price tag.
Additionally, a plug computer uses 5 watts under normal operations, in contrast to the typical 25 to 100 watts for a dedicated PC.
What can you possibly do with such a small device? Ahh, this is where Linux shines.
First things first, you won't run Microsoft Windows on this gadget. Not even Windows 7 Starter edition will fit or the aging, but popular, Windows XP.
Linux does the job admirably, with even the most full-featured distro like Debian being able to slot into the flash memory provided you're economical with what you install (scrap Gnome and KDE for starters!). Or Damn Small Linux and other distros of its ilk will do the job just fine too.
Linux has always had a stellar reputation for its server capabilities and while plug computers aren't powerhouses they can serve as a tremendously compact, a remarkably discrete and even super-portable network server.
The miniscule form factor and low power consumption mean you can hide a wall wart virtually anywhere in your home or business without concern that it runs 24x7.
The gigabit Ethernet and on-board USB 2.0 means the device could be a media server, a file server or print server for your network.
You could assign it a public static IP address and allow it to be your SSH gateway from the public Internet using wakeonlan to bring other internal computers on line as you need them.
While I'm a big advocate of DropBox it's not for everyone; some people prefer not to share their files to the cloud. In that case, set up a wall wart and USB hard drive as your own private FTP server, accessible from any location.
Of course, you can even run your own web site using Apache on a plug computer. Run your own simple site, or run a site to monitor other sites! If you're a professional web designer or otherwise responsible for the uptime of web sites check out PHP Server Monitor which will test a list of web sites and servers you specify and message you if something is down.
Obviously, these few possible applications I've described could apply to any server. There's nothing specially, well, wall-warty about them.
However, that's part of the point; plug computers are real servers and do real things, provided you can conceive it. The difference is they're ridiculously tiny and staggeringly cheap.
Finding plug computers is a bit trickier than walking into your local retail store, but UK retailer NetIT sells the GuruPlug and SheevaPlug with varying options that expand the units with WiFi, Bluetooth, SD, microSD and eSATA ports, not to mention Linux pre-installation.
Scaling up to a larger size the Pogoplug is presently available in the US for a $30 rebate off its usual price of $US 99.99. The PogoPlug is specifically marketed as 'the easiest way to share files and multimedia' over the Internet.
Will your next computer purchase be a Linux-based plug computer?