I\'m quite confused with what are the necessary tools for VSTO develpment. Specifically I want to manipulate Excel 2003/2007 documents programmatically. I did quite a lot of
SpreadsheetGear for .NET is an Excel compatible spreadsheet component for .NET which will work with Visual Studio Express editions, requires .NET 2.0 or higher, does not require Office or Excel to be installed, and does permit royalty free distribution to an unlimited number of client and / or server computers.
You can see live samples here and download the free trial here.
Disclaimer: I own SpreadsheetGear LLC