This falls under the optional category for many of you but I highly suggest looking into equipping your setup with one per machine or a larger unit capable of serving multiple machines. A lot of people neglect their power supplies and battery backup units to save money. I find this to be a rather poor decision.

A UPS acts in the same way as a battery on a laptop. The power goes out and the battery instantly switches on - your system stays online. They also condition the power going into your computer and can correct for over or under power situations, as well as protect from surges through power, phone and cable lines.

For a single system, a single UPS (Uninterruptible Power Supply) can run around $50 to $75 - but even if your power is stable and rarely tends to go out, you will appreciate owning one when it does happen.

I suggest going with APC, one of the most well known brands out there. For single systems, they offer models that connect via USB.

A few caveats.

Of note for multiboxers: larger 3 or 4U sized units are fairly inexpensive (check ebay for local auctions) but may need battery replacements - they are usually only good for 3 - 4 years. However, such a system may be able to protect and run 2 - 3 normal systems and LCD monitors for 10 or 20 minutes.

If you do buy one of the larger models - do not plug a normal serial cable into it. It will literally short it out and power down the entire UPS. This is the dumbest design feature ever. Plans are available to make a special cable or simply buy one from them. Also, note that their software sucks. Horribly. For some reason they offer three levels of software. Free, basic home use. Free and Pay Business use and $2,000+ Network Datacenter use. None of the versions communicate with each other. The pay business will not read the cheap USB model you obtained. For casual monitoring - you can probably get away with a standard free version.

If you want to be able to chart battery life, runtimes remaining, power events, etc - open source has come to the rescue. Take a look at APCUPSD http://www.apcupsd.org/, an open source version that far exceeds APC's version for flexibility. Setup is a bit tricky (need to edit some config files) but once you get it going, you can setup custom CGI graphs, load up gapcmon (a Gnome based Linux (think Ubuntu, Debian) plugin) support for unlimited numbers of devices, etc. Real fun stuff.

For those of you with multiple UPSes from different vendors, NUT Tools may be of some help. I have not personally tested it but it seems like it is moving along well. http://www.networkupstools.org/