I have a corporate rate from UPS that works well for international -- it is usually about 60% of the published rates. HOWEVER they are extremely finicky about the shape of packages and "dimensional weight" and will slap you with big excess charges if you don't toe the line. I use them for only special situations where the package is relatively short in length and I can get it down into a box that is I think less than 3" x 3" (width/height). Obviously this is rare.
Domestically I use Fedex Ground for big packages including big oversized heavy tubes. I have an account with them so get about a 15% discount (not a corporate rate), and it's worked out pretty well. And their web site for shipping is just light years ahead of dumpy UPS.