If you are planning on mailing out some bills or letters this weekend, don't put it off. Saturday is the last day that postage stamps will cost 46 cents. Starting on Sunday, the cost of a stamp will go up to 49 cents.The 3 cent increase is the largest increase in consumer postage prices in more than a decade.

You can buy Forever Stamps at the current price at 46 cents, until Saturday, and use them after the rate increase on Sunday.

Forever Stamps have become very popular: In 2012, 21.8 billion of them were sold, making 84% of stamp sales.