Post from USA to BELGIUM

The cheapest is almost always the USPS (the normal postal service). Some of those places that offer services from FedEx, UPS, and DHL also offer USPS services so they can do comparison pricing. Something like Mailboxes Etc but can't remember exactly the name of the shop. Call ahead for a place like that before you make the trip. Don't forget that the person receiving the box will also have to pay an amount to the Belgian Post.