Front USB ports
I installed just what you are talking about a few weeks ago.
I bought a unit that fits into a 3.5" bay and provides three new USB ports in the front. But wait, thats not all! It also included a PCI card that slips into a empty slot and adds two more USB ports in the back! So I got five more ports, three front and two back. And I still have my orginial 2 in the back so now I have a total of 7!
I saw the ones the previous poster show that requires a USB cable connection, but I like the way mine installs with a PCI card.
I found mine on eBay and I paid something like $24 plus shipping.