UNDATED (WKZO) - The United States Postal Service expects today to be its busiest mailing day of the season. An estimated 655-million cards, letters and packages will be processed nationwide, according to postal workers.

They're reminding customers that an expedited process is available at most post offices by using the self-service kiosks, which are available 24-hours-a-day.

Meanwhile, Good news for online holiday shoppers: Today is Free shipping Day. The sales promotion idea was introduced four years ago with a website dedicated to letting people know where they could find free shipping deals.

This year, more than 12 hundred merchants and online retailers have signed up to take part in the event. Free Shipping Day is the brainchild of Luke Knowles who says the goal this time around is to at least tie the online sales numbers seen on Cyber Monday.

Last year's Free Shipping Day event generated over a billion dollars in online sales.