Postal Rates as of 2008 - Priority

  Priority is the only reasonably priced shipping left for international packages.  Any international package 4 pounds or less should be shipped first-class.  The only exception is when shipping an item between 1.3 to 4.0 pounds that is flat, it might be best to use a priority flat rate envelope.  All packages between 4 to 70 pounds need to go priority. Special rates are available.

These rates are:

Flat rate envelope;
Canada               9.95
 International     11.95

Regular flat-rate box;
Canada              23.95
International     38.95

Large flat-rate box    
Canada              29.95
International     49.95

  My suggestion is use a regular flat-rate box when you have an item over 5 pounds.  Use a large-sized one when shipping an item over 9 pounds.

  For domestic priority:
 Any item over 13 ounces needs to ship priority or parcel post.
Rates are;
 Envelope        4.80
Regular box     9.80
Large box       12.95
 
  If not using these boxes consult a rate chart from USPS.com.
These shipping containers have the following sizes;
Envelope:             12.5 by 9.5 inches
Large box:            12 by 12 by 5.5 inches
Regular box:         11 by 8.5 by 5.5 inches
or 13.6 by 11.8 by 3.3 inches