The clock is ticking for those who still haven't sent out their holiday gifts.

If you're shipping with the United States Post Service, Saturday marks the last day to use priority mail. This will ensure that a package reaches its destination in one to three business days, starting at a price of $7.50 for shipments within the continental United States.

You can still use priority mail express shipping until Dec. 23, which will guarantee a package arrives in two days. This costs $26.95.

The deadlines for United Parcel Service are Dec. 21 for three-day shipping, Dec. 22 for second-day air shipping and Dec. 23 for next-day shipping.

Those really in a scramble can get their gifts delivered on Christmas Day from FedEx with its city direct, city priority or same-day shipping options.