FedEx will not accept live animals from an individual so most folks go through a third party to ship. The two big ones are shipyourreptiles.com or reptilesexpress.com. I've used reptiles express several times and their customer service has been nothing but outstanding.
I'm not sure about reptiles and USPS. I haven't seen anyone shipping reptiles using them but not sure if they can't or don't. I'm assuming there's a reason you can't or some folks would? Maybe some one who knows will chime in
I've had and seen too many casualties when shipping fish with USPS. Very recently, I had a fish come in a day late and crushed to death, after talking to the shipper (an Internet friend) and having the fish lined up for months. It was her first shipment ever, and I felt terrible that she started her shipping off like that. A few weeks before, an other Internet friend had their package of snails crushed. Thankfully their snails all made it when my goldfish wasn't so lucky. I know UPS is very strict, but I've not ever seen or heard of any issues with them.
US Postal is going to give you the poorest and most unpredictable service. I don't recommend shipping live reptiles through USPS.
ShipYourReptiles is a FedEx service. Without our service, you need to be individually certified with FedEx to ship live reptiles. With ShipYourReptiles, you are shipping under our certification. You also agree to meet our SYR Shipping Standards, which meet or exceed the FedEx standards (standards include insulated box requirements and temperature parameters).
Shipping with FedEx directly, you are only allowed to ship to and from business addresses (zoned as businesses). With SYR, you can ship to and from residential addresses as well.
ShipYourReptiles is the only service that offers On-Time and Live Arrival Insurance. We also offer a micro-donation function in the booking process to allow you to donate as little as 50 cents per shipment to USARK and PIJAC, to protect the future of not just shipping reptiles, but keeping reptiles period. We have raised thousands of dollars this year, and should break $10,000 for the 2014 year, just 50 cents at a time. Awesome.