ClosedXML makes it easier for developers to create OpenXML files for Excel 2007. It provides a nice object oriented way to manipulate the files (similar to VBA) without dealing with the hassles of XML Documents. It's developed in C# but can be used by any other .NET language.
What can you do with this?
ClosedXML allows you to create Excel 2007/2010 files without the Excel application. If you ever used the Microsoft Open XML Format SDK you know just how much code you have to write to get the same results as the following 4 lines of code.
var workbook = new XLWorkbook("Sample.xlsx");
var worksheet = workbook.Worksheets.Add("Sample Sheet");
worksheet.Cell("A1").Value = "Hello World!";
workbook.Save();
Development Status
The current build has the following simple capabilities:
Can create new workbooks
Add worksheets
Access cells using R1C1 and A1 notation.
Add text, dates, booleans, and numbers to cells
Select ranges (not named ranges though)
Traverse a range's columns and rows
Read more: Codeplex