You only have today and tomorrow to mail letters and parcels for 39 cents. Beginning Monday the rate increases to 41 cents.

Because most post offices are closed Sunday, officials say items dropped in a box that won't be collected until Monday should have the higher postage on them. However, the agency doesn't plan a rash of returns for insufficient postage.

And you can always buy "forever" stamps that remain valid regardless of any future increases. The first forever stamps are selling for 41 cents each.

And people sending heavier letters -- such as wedding invitations -- will see a reduction in the price. That's because each additional ounce will cost just 17 cents, down from the current 24 cents.