SIIG SuperSpeed USB 3.0 Bay Hub+Host Kit does its job and does it well. It adds four front USB 3.0 ports to your rig without needing to snake cables outside your case. It is however limited by its PCI Express x1 interface.
Asus U3S6 is a potent upgrade path for anyone not wanting to go through the hassle of upgrading a motherboard. Just be prepared to ignore the included SATA6 ports unless your motherboard is on the ASUS qualified list.