Informed Delivery is a cool new service being rolled out to residential customers across the USA. It allows you to see (in a daily email) a picture of the outside of all envelopes about to be delivered to your mailbox. Although it's a bit creepy (but not surprising) to know that "big brother" is watching your mail, this is a useful service if you are out of town for a while and don't want to miss a wedding invitation or something important.
You can now receive an email with a picture of all letters that are about to arrive in your mailbox.
This is the official website with all the details you need
If your traveling anywhere in the USA and need something mailed to you, it's easy to have the package (or letter) sent to almost any Post Office. You simply address it like this (example):
TAMPA BAY, 33602-9999
When you get to that Post Office, simply go to the desk and present your ID and they will give you your letter.
General Delivery is a service that makes it possible to ship something to someone who doesn’t have a mailing address or even a post office box in a ...
This blog post has a good overview of General Delivery with all the details you need