We run an oscommerce store with three shipping options (USPS, UPS and DHL). We want the user to be shown when each shipping option will ship (i.e. next business day if after the shipping cutoff or today if before the shipping cutoff) and when it will arrive.
This store - [url removed, login to view] - has exactly what we want (add something to your cart and proceed to checkout to see it).
Calculating when the ground deliveries will arrive does not require precision (i.e. it can say 2-4 days).