The US Postal Service has entered the 21st century ;) Though I haven't personally used this feature yet, apparently you can order and pay for parcel service online but most importantly you can set a time for the USPS to come pick it up at your house—all free of charge.
I did spend a little time on the site which appears to target small business owners. For the most part it seemed fairly clear and intuitive. This might be a good option for those of us who dread going to the post office—especially around the holiday season.