Media streaming, network backups, assorted virtual machines (web, Minecraft, cloud storage): 3.7GHz hexacore Intel i5, 64GB RAM, Windows
Quake, Ventrilo, QTSS: PowerMacintosh G3 / 350MHz, 896MB RAM, Mac OSX Server (Panther)
NG Firewall/Router: Custom built AMD Phenom II x4 3GHz, 2GB RAM, Untangle OS
These systems are currently in full-time operation. I've done what I can with what is essentially a mobile setup.
I've found no point in further cable management / accessories until I have a house and a more permanent setup, thus the shorter rack on casters. Makes moving easier.