SharePoint Designer 2010 is the tool of choice for the rapid development of SharePoint applications. Using SharePoint Designer, advanced users and developers alike can rapidly create SharePoint solutions in response to business needs. Advanced users can compose no-code solutions that encompass a variety of common scenarios, from collaborative sites and web publishing to Line-Of-Business data integration, business intelligence solutions, and human workflows, leveraging the building blocks available in SharePoint in an easy to use environment. In addition, developers can use SharePoint Designer 2010 to get a quick start on SharePoint development projects.
For additional information, please refer to: Microsoft Sharepoint Designer: LSU Overview.