I find USPS still sometimes delivers Amazon packages, especially their Slow Spiteful Shipping or No Rush shipping (when they've relented and given you "Prime").
There is also UPS Surepost and Fedex Smartpost. AFAIK these are all charged at a lower rate for dropping pre-sorted packages off at the local PO for last-mile delivery. But of course such last-mile delivery is the expensive labor-intensive part.
