I like to build my own PCs, but generally when I build them I am more interested in making them perform well than look cool inside. What that means is that I am too lazy to clean up the wires and put in cool stuff like lights. I did try adding lights to a PC once, but they CCFLs were so large it was hard to find a place to put them.
Normally if we are talking about NZXT were are looking at a new PC case. The company does offer a full line of cool accessories though and the latest is a new Sleeved LED kit. The sleeved kit puts a bunch of LEDs into strips that are offered in 2M or 1M lengths. Each strip can be had in five different colors.
These colors include red, green, white, blue, and orange. The sleeves the LEDs are inside look like the material that the cables from most PC power supplies are covered in. The strip is flexible and easy to cram inside the nooks and crannies of a computer case. A dimming control is also included with three settings plus the ability to turn the lights off.