Casejunkiez has a little guide up on how to clean up the innards of your computer.
Here's what they have to say.
I toyed with the idea of hiding all the wiring in the case, but that would
have been a huge lesson in patience and heartache. In the end, I tried a few
different things and worked out a nice little mod that keeps fan wiring and
the likes looking neat as well as looking pretty nice at the same time.