To get
Look here
Visual Studio Web Part template
Search http://www.microsoft.com/downloads/ for "Web Part Template."
Excel Office web part add-in
Search http://www.microsoft.com/downloads/ for "Spreadsheet Web Part."
Office web components (client)
Search http://www.microsoft.com/downloads/ for "Office Web Components."
Office web parts (server)
Search http://www.microsoft.com/downloads/ for "Office Web Parts."
Spreadsheet web part schema documentation
Office web component object model (VBA)
http://msdn.microsoft.com/library/en-us/owcvba11/html/ocwelcome_hv01136208.asp