<p>I am working on an ASP.NET MVC application where I need to export data to an excel spreadsheet.  Previously, in webforms apps, I used some code I found to render a GridView as an excel-compatible file.  This was quite handy. I was wondering what the quickest/most effective method would be to do this in MVC. Thanks.</p>

One simple option would be to create a view to render an XML-version of an Excel File. You could either use the new Office 2007 version, or the older 2003 version. We chose the 2003 version so that more people could use it, but that's up to you, of course.
XML 2003 ref on MSDN
XML 2007 ref on MSDN