Loading a 500GB drive with USB2 or Firewire is going to take all day.
If you have eSATA ports, I highly recommend using them. If you want an external enclosure, I'd recommend something like the:
Thermaltake Max 4
Antec MX-1
With those two you have eSATA for speed, and USB if the guy you're sending to only has that.
Personally, I like to use mobile racks. I have stacks of HDDs here and I can just hot-swap them in as needed:
Kingwin KF1000-BK
For the drives themselves, I like Western Digital, although Seagate has better warranties.
Good luck!