Shipping large, but not heavy item...

Can you transport it to a Mailboxes, etc?

Check the local newspaper add where there are some adds about freight deliveries. At the same time place a newspaper add into the same newspaper or several ones and there is a possibility that you'll get the responce from cruising trucker that will pick up your freight for less. I believe that no truck driver will refuse extra $50 for the rest of freight he/she delivers. If you will decide to speak directly to the driver's team of a certain trucking company make sure you speak ONLY to the drivers and not to dispatcher or the owner that might prohibit driver to take some extra-cargo off the company. You've got to make sure that you'll arrange the payment upon delivery as well.

I have used both of the below methods successfully:
If you can locate a local freight trucking firm then you can hand carry the item to their facility. Have the receiving party make arrangements with any commercial firm for permission to have the box delivered to them at their commercial address (the truck WILL deliver there). The receiving party can then pick it up directly from there.

Another alternative is Greyhound Bus Lines. You hand deliver the large package to a Greyhound terminal in your city & have it bussed to another Greyhound terminal at the receiving end. Again the receiving party can then pick it up directly from there.