I have set up an account - it's free for Ebay users but it won't draw info from PayPal webstores - it will import data from Ebay, or you can enter info manually. There is a slight discount for international orders, but I suspect it's not as good as Ebay's discount. Nonetheless, it is better than PayPal, which does not allow international packages.

I have discovered that I can cut the address from my PayPal record of sale and paste it into Stamps.com as an entire address (which is far better than the post office Click-N-Ship software where you have to do it line-by-line).

This should be a good stopgap while I research services that integrate payment and shipping (without monthly subscriptions).

Thanks for the added comments - it's good to know it's working out for others, too.