Actually, I just now (20 minutes ago) installed a VIA 6220 PCI USB2.0 card. It was a bit of a hassle because the card doesn't quite fit right, and it was at one point conflicting with my soundcard, but it works now.
The reason that I got a PCI card instead of just a hub, is that my two on-board USB ports appear to be dying and I didn't want to plug a hub into what could be a non-working port tomorrow. If you have functional on-boad ports, just get a hub -- it's slightly cheaper, and less hassle.
