This little device qualifies as one of my best impulse purchases to date. For under $30 I now have a full Debian Linux system running 24/7 that uses about 4watts of power.
One thing to mention is there are many different versions of the Pogoplug. The model I am using is POGO-E02, which sports a Marvell Kirkwood 1.2GHz ARMv5te Processor, 256MB Ram, 128MB Nand, 4 USB Ports, and Gigabit Ethernet. I splurged with a 16gig Flash Drive to be my boot device and main storage.
Out of the box Pogoplug allows the user to add external hard drives via USB, which are then made available both locally and over the Internet. However, thanks to the effort of many individuals, there are two prominent OS replacements which can be loaded to expand the capability of these devices. Arch Linux ARM is a popular choice, supporting many of the Pogoplug devices and backed by an active community. Debian Linux has always been my preferred distribution, so I was happy to find there was support for my particular model.
Jeff Doozan hosts what seemed to be the definitive guide to installing Debian onto a Pogoplug device. However, I found out during install that due to updates at Debian some of his scripts were now out of date. Luckily, another forum user Shyd was able to modify the install script to support the latest stable release, which at this time is Squeeze.
After running the script you are presented with a base Debian install to do with as you please. I configured some default options as suggested by Luke, and then installed Lighttpd, PHP5, and MySQL following this guide. Lastly, I took some ideas from mewbies to customize my shell MOTD to display prominent information at login.
I am very pleased with the results and would recommend this as a great low cost learning solution to anyone wanting to dabble in the world of Linux.