Using the USPS flat rate boxes which allow you to ship almost anything regardless of weight for a flat rate is a great way to ship that birthday present, graduation gift, or Holiday gift.
Since the USPS have put in the self help kiosk you can come anytime day or night and get that package mailed. I found I don't have time during the day to stop in and mail something, so using the kiosk and flat rate boxes allows me to pop in any time. If you go to the main office on Sunset by the airport, you can bet that package will go out quickly.