SharePoint Extensibility with Excel Web Services

SharePoint 2007 supports an extensibility mechanism using Web Parts.

ASP.NET Web Part controls are an integrated set of controls for creating Web sites that enable end users to modify the content, appearance, and behavior of Web pages directly in a browser.

Excel Services is part of Microsoft Office SharePoint Server 2007 which is built on ASP.NET and Windows SharePoint 3.0 technologies. Using Excel Web Services we can create Web Parts which can be dropped into SharePoint and add custom functionality into it. More Here Using Excel Web Services in a SharePoint Web Part