We love our IKEA SIGNUM cable box. It does a great job of keeping wires and cables out of sight (and was very affordable). But it also seems to have been discontinued. The Bluelounge Cable Box is a handsome and affordable option, but may not match every decor with its minimalist-modern form...
HideMyCables.com is a site that offers custom built wood boxes to hide your cable and wire mess for home theaters, home offices and anywhere you might want to hide tech mess. Boxes start at $50 and can be made from 3 feet to 6 feet, in pine and oak, and offered in natural or ten different stains (your options affect the price) with a 3-4 week order turnaround. Not bad for a custom ordered piece. Hmm, one of these might go well complementing our rosewood vintage stereo cabinet...