Scott Hanselman's ComputerZen.com

There's a number of ways to "export" data to Excel from an ASP.NET site - some more elegant than others.

• Gross: You can use ASP.NET to generate a CSV file of Mime Type text/plain or text/csv and write it back to the browser.
• NOT Gross: You can use ASP.NET to generate an XML-SS (Excel XML Spreadsheet) document and write it back to the browser.
• Really Easy but not Really XMLy: You can take advantage of the ASP.NET DataGrid's ability to generate HTML tables quickly and return the page with a Mime Type of application/vnd.ms-excel.  Here's a great example on how to create these reports. 
• Easy but uses 3rd Party Control: Use ExcelWriter on the server side to create the Report.
• Disgusting: Automate Excel on the ServerSide.  Don't do this for Pete's Sake.