Stamps

From The PirateBay-FreeNationFoundation Wiki

It is not yet known if Sealand will support a postal service, and need stamps.

Here's an idea - have someone maintain an address in another country (possibly the closest) and use that address to receive or send letters and packages. A boat or plane would make a daily trip to and from the island with the mail - this could be called The Pirate Express. This solution would eliminate the need for a postal service or special stamps and would also eliminate excess shipping costs in case someone decides to order a new motherboard..