The UPS webservice is a lot easier to deal with than FedEx is. Or at least that was the case when I wrote the fancy webstore and order fulfillment system for Taylor Shellfish half a decade ago. With UPS, you can get all varieties of rates and availability for a set of boxes in one request. FedEx required one separate request for each different service, from what I kinda remember. I hope they fixed it since then. (BTW: Taylor Shellfish changed to a different web design company that replaced their fancy webstore that we made with some cookie cutter junk. What they have online now wasn't my doing.)

I have some very nice code that does all kinds of UPS stuff that I should have made into a proper module (tests, etc) long ago. I don't even know if I can find that code anymore. If I do, I'll see about releasing something on the CPAN. I'm not sure releasing a separate module would be better than enhancing the modules already on the CPAN though.