Sending a letter is going to cost a penny more tomorrow. The same goes for postcards.

First class mail to Canada or Mexico is going up 3 cents.

But not everything is rising.

Forever stamps will still be valid -- even those bought months ago at the 41 cent-rate. A 42-cent Forever stamp will be on sale at post offices beginning tomorrow.

Online customers, those using Priority Mail, bulk users and corporate account-holders with the U.S. Postal Service will see discounts.

Depending on the ultimate destination, Express Mail customers also may see a decrease.

It's all in an effort to recoup costs, as well as be competitive in the marketplace, said Frances "Fran" Sansone, a regional communications coordinator for the Postal Service.

A penny, you see, adds up.

For the 130,000 customers who receive mail bills rather than electronic bills from the Richmond Department of Public Utilities, that means an additional $1,300 will be spent each month to tell customers what they owe. For the Postal Service, it means an additional $3.16 million per day collected from customers to process first class letters.

For the nonprofit group ChildSavers, which provides mental-health and childhood-development services, stamps for thank-you notes alone could rise by $1,400, which has a budget of $3 million.

"We're probably going to have to be more creative about how we reach out," said Lynn McCashin, director of development and community relations for ChildSavers.

Much of the increase comes down to the price of gas. The Postal Service, with 219,000 vehicles, operates one of the largest fleet of cars and trucks in the world.

Every penny rise in gas prices causes the Postal Service to spend $8 million more per year in fuel costs, Sansone said. Gas prices increased 31 cents in the last month in the Richmond area as of Thursday, which translates into $2.48 million in additional fuel costs.

"It's tough and just like any other business, that's part of the expenses that hit," Sansone said. "Fuel costs are a big, big hit."

The Postal Service cited fuel costs as one reason why second quarter expenses increased by $52 million, or 0.3 percent, when reporting the results Wednesday. The service reported a 3.1 percent drop in mail volume for the second quarter to 51.3 billion pieces because of declines in the housing and credit industries, which are heavy mail users.

The increase in the cost of stamps will help the postal service maintain operations, but it could affect others.

Nonprofits that don't use third-class mail, which takes longer than first class, will have to spend more to send out solicitation letters.

"It ultimately means that's an extra penny [nonprofits] can't spend on programming," said Deborah Williamson, executive director of Virginia Network of Nonprofit Organizations. "They can't easily recoup that cost by raising the fees or getting new sources of revenue."

Some businesses have opted for a more advanced way of communicating or doing business because of cost and timeliness.

Scott Shaheen, regional vice president for Long & Foster in Richmond, said agents are careful where they spend their marketing dollars because every increase affects the cost of doing business.

"In the days of the electronic age, we've moved to fax and e-mail as much as possible," said Shaheen, who also is president of the Richmond Association of Realtors.

A law passed in 2006 authorized the Postal Service to raise rates each May for stamps but the increase can be no more than the Consumer Price Index inflation rate. It also gave the post office the right to change prices for competitive services, such as Priority and Express Mail based on market conditions.

Here are some of the changes: