Depending on what you're shipping/quantity USPS is a good value with it's flat rate priority shipping. Package it well enough and it is virtually failsafe.

If you were shipping quite a bit of precious cargo and were to use UPS just be sure to ship ground. Depending on your shipping location and destination the package will pass through 8-12 hands a split second at a time and there are no dogs on the ground. Put it in a decent sized clean-cut looking box and there is very little chance of it being inspected, damaged or lost.