Original member gets the shipping upgrades, videos, Amazon Mom & lending library.
Additional members get shipping upgrades only.
Each Prime account can have 4 additional family members associated with it.
Amazon adds bennies to prime accounts so this list may change - feel free to update the wiki if you discover new information.
To add yourself to an account: You need to provide the original member with your name, email and month/date of birth. Do this via PM.
The member will respond back with the info you need to complete your signup.
When signing up with someone, make sure you know how long the prime membership will last first, to avoid any misunderstandings.
You may also want to check if Amazon charges tax in your state before you make up a price. henche's family method
Split the above with your siblings and cousins. You can share passwords and just need to remember to charge the correct cc and ship to the correct address. This way you can all use the video streaming also.