I have been using US Air Cargo for years with great success. It's very simple to do. I usually just call their 800 number (1-800-468-7247) and pre-book all of my shipments. This allows me to get an airbill number out to my customers a few days in advance.
When you call tell them that you would like to ship harmless snakes via PDQ and you are not a known shipper. You give them the two airports and the day you want and they will work out the best flight (most direct) for your shipment (you also need the consignee's name, address, and phone number). I always tell them I would like cargo to cargo instead of having to go to the counter inside the airport (I figure less chance of the box getting lost this way).
Their website has directions to the cargo facilities at each airport (
http://www.usairways.com/cargo). You need to get to the cargo center 90 minutes prior to your flight with your box unsealed to they can inspect it (security measure, and usually very painless). You can pay right there or send it collect. Their customer service is always fantastic.
If you pack your box correctly with heat packs and stryo lining your snakes will do fine.
Hope this helps.
-adam
ps ... I am not sure what they do about venomous snakes, not my thing.