The local postmaster.
Standard mailboxes for depositing outgoing mail are blue.
sometime on mondays-sundays
Yes, anything under 13 ounces can be put in the mailbox
The United States Postal Services owns all the mailboxes into which the USPS delivers mail. The USPS contracts with private vendors, like Mailboxes Etc. or the UPS Store, which rent mailboxes that consumers can use for mail delivery. The laws apply as with any mail that goes through the U.S. postal service.
Essentially any mailbox you buy has to pass USPS regulations or noone would or could sell it. If you sold mailboxes that didn't meet standards you'd be in a lot of trouble. Most of the regulations relate to moving your mailbox or the post. Advertising is not allowed on the stand or the box. Full regulations can be found here. http://www.usps.com/receive/mailboxstandards.htm
There are many mailboxes and posts located in Washington DC. The best way to find the one closes to you is to go to the United State Postal Service (USPS) website and click on the location finder. The closest 50 will be listed for you once you put in you zip code.
USPS Consumer Affairs
Private rural (roadside-type) mailboxes - some locations DO have parking regulations that prohibit this. If they are official USPS roadside (drop off mail from your car-type) boxes, yes, illegal and you can get a ticket. As far as US Postal regulations are concerned. . . they are not required to deliver the mail to an obstructed mailbox.
buddy, where are you living?
It depends on who you ordered it from. If you ordered it from another person via eBay, CraigsList, etc., then it will probably come by UPS, USPS, or FedEx. If you ordered it from a store, it will most likely come by UPS or FedEx.
5days longer than you want to wait
Various vendors with Amazon may use FedEx, UPS or USPS to ship items ordered.