How large is the box you want to ship?  Is the box made of cardboard, or is it a large wooden box, or something else?
assitant
You can use Media Mail for small parcels, less than 1 pound in weight, to ship throughout the US and internationally to Mexico.  This option will be more expensive than those I mentioned earlier, and also may require sending insurance with the package.
assistant
Which shipping carrier is cheaper for shipping packages?
user
Which package do you want to ship, and where to?
assistant
I want to ship a box of books to Texas from Maryland.
user
If you go with the least-expensive service, Federal Express should be the cheapest option, around $20.  If you ship within the continental United States, UPS or USPS are similar, and would be less than $25.  Or if you are willing to pay more, you could ship with the United Parcel Service, which will be more expensive.
assistant
I heard about using Media Mail from USPS. I think I can ship books cheaper if I use that service.
user