Domestic
Media Mail: $5 for first item plus $1 for each additional item
Overnight: $15 for first item plus $2 for each additional item
2-Day Air: $12 for first item plus $1 for each additional item

Foreign
Surface: $5 for first item plus $3.50 for each additional item
Airmail: $12.00 for first item plus $3.50 for each additional item