The new (mostly increased) prices of the Post Office go into effect May 31, 2015, and they finally came out with their new up-to-date "Notice 123 Price List," which is their complete price list (charts and all) for domestic and international mail pieces.

The first thing I looked at is the minimum retail (clerk at post office) rates for parcels/small packets:
¶ domestically, a 1-3 ounce parcel rate increased from $2.32, to now $2.54.
¶ internationally, a 1-2 ounce parcel (to any country) increased from $6.55, to now $7.10.

It is a good idea to bookmark this useful price list (domestic and international):
http://pe.usps.gov/text/dmm300/Notice123.htm#1118064
Here are some pictures I made from it:

Among the neat things in Notice 123 is a list (with dimensions) of all the free mailing boxes (flat rate and non-flat rate) that the Post Office furnishes.

Incidentally, "Retail Prices" are what you pay the clerk at the post office or if you put stamps on the mail piece. "Commercial Prices" are what you pay if you print your postage labels on your computer.

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You might want to bookmark this too, a handy Postage Price Calculator (domestic and international). It also lets you know what insurance and custom forms are required/allowed:
http://postcalc.usps.gov/

Robert
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Gary Cooper (center) in "Along Came Jones" (1945).
http://www.antiquegamblingchips.com/StillsA_TopMaleStars.htm