I sent our 8 UPS ground - they were delivered the next afternoon.
I chose UPS because of the size of the box with 8 blankets, and because tracking and confirmation is more reliable with UPS scanners than with the postal service confirmations - at the office, we've used postal service priority with confirmation in the past and had items be reported as delivered when in fact they weren't... and we received them back a few days later. The cost for my huge 8-blanket box on UPS ground was about $13.