Thanks for the great info, that really clears things up. The Stamps.com desktop program looks like it will work very well, and will let me print labels in both 4x6 and 2x7 sizes, or in smaller sizes for about a dollar more per package.
Since my boxes are actually 4x2x2 (I posted the wrong size earlier), I will need to wrap my labels around 3 sides of my boxes. Is this allowed?
Once I’ve paid for and applied the label, can I just drop the box into any nearby blue USPS mailbox to have it shipped?
I am also a bit curious about international shipping. The Stamps.com program says that I can ship via First Class International for $4.16, but says “Large Envelope”. The USPS postage calculator (http://ircalc.usps.com/) says that a 3oz package will cost $9.45. Any tips on basic international shipping?