E-Commerce Shipping Solutions?

[McKirahan]

I am developing a shopping cart application and would like to determine
(based on weight, dimensions, and destination) the actual shipping
charges that USPS, UPS, FedEx, DHL, and/or Airborne would charge.

Each shipper has APIs that support this functionality...

E-Commerce Shipping Solutions
http://www.nfib.com/object/1583793.html

Does anyone have or know of any information about doing this.
I'm hoping to shortcut the learning curve by leveraging the
experience of others.

This is for a not-for-profit that will be selling a few products.
Hopefully to numerous customers around the world.

Thanks in advance.