Kind of like Lyft, but for your packages, Barnacle hooks you up with people who drive long routes and will accept a little extra cash to deliver your packages on their way. Alternatively, you can deliver packages for others and make some money yourself.
All you do is sign in via your Facebook account and search for people going between you and your package's destination. From there, you offer them a fee of your choosing and they'll accept the job if they want it. How long it'll take your package to arrive at its destination will depend on when these couriers-for-hire are making their trips, but from what I could see it was generally a week or less. Plus, you can track the location of your package at all times through their smartphone apps.
While not an alternative to expedited delivery services, it's a nice way to save money on slower packages—especially larger ones. The service is pretty new so only so many routes are available, but given that there are quite a few. And, should you want to pick up some extra cash you can sign up to drive as well.