One of the problems with having a lot of accessories plugged in around your computer is that even after you turn everything off they're still draining power. Instructables user schubertj wanted a way to automate the powering off of his speakers, monitors and printer, so he hacked a USB into a power strip so it's powered by the computer itself.
Using a set of supplies totaling around $US30, the basic premise is pretty simple. When the computer powers on, the USB sends power to the power strip and the rest of the devices turn on. When the computer is powered down, so is the power strip. As you'd expect, this is a pretty complicated project that deals with high voltage so you have to be careful, but the end result is a nice automated system that will help cut down your power consumption by looping everything together. You can find the full guide for the project over on Instructables.
Computer Controlled Power Strip [Instructables]