What is the best way to ship items?

Online postage tools.   USPS.  eBay.  PayPal.   Stamps.com. And many more.....

you get special online discounts on Express Mail®, Priority Mail®, and access to free Carrier Pickup™. The tool is free to all registered USPS.com users. No monthly fee. No proprietary software, or hardware. No special paper.

Free:

Delivery confirmation.
Hidden postage.
Package pickup.

And much...much....more!


https://www.usps.com/business/online-postage.htm

Other options:
Greyhound-  www.shipgreyhound.com
Amtrak-  http://www.amtrak.com/servlet/ContentServer?c=Page&pagename=am%2FLayout&cid=1241267371736


And for some decent priced shipping supplies if you for some reason need 50 boxes at once....

shippingsupply.com/