USPS rates calculator

The USPS Web Tools allow developers of web-based and shrink-wrapped applications access to the on-line services of the United States Postal Service (USPS). They provide easy access to shipping information and services for your customers. Your customers can utilize the functions provided by the USPS without ever leaving your web site. Once the Web Tools are integrated, your server communicates through the USPS Web Tools server over HTTP using XML (eXtensible Markup Language).