If you've bought any hardware in the last six months, chances are some part of it either has built-in RGB LEDs or a connector for an LED strip. I know a lot of gerbils don't share my affection for the blinkenlichten, but if you're coming around to the dark light side, check out CableMod's new WideBeam Hybrid RGB/W LED strips. As the name suggests, they combine RGB LEDs with pure-white LEDs.
The bright white light is perfect for showing off your killer cable management job, and lighting like this could come in handy when you need to make a quick change inside your case. Kidding aside, one of the biggest complaints with RGB LED lighting is that the "white" generated by shining all three colors at maximum brightness never looks quite right. These strips address the problem by simply sticking a pure white LED in each cluster.
When you want to use pure white lighting, you can just use your control device's software to change colors. If you're using the strips by themselves, then you can use the included 40-button wireless remote to flip through shades. As an added bit of convenience, the remote uses RF signaling rather than infrared, so you don't have to worry about sticking an IR blaster on your case somewhere. The strips get their power from a SATA power connector, and all of the relevant wiring is included with the one-foot (30 cm) or two-foot (60 cm) strip of your choice. Alternatively you can purchase either style separately.