Add advanced spreadsheet capababilities to your applications. Perform calculations, reference cells with relative and absolute addressing, perform formatting, handle multiple worksheets.
Solution Center - Code examples using Spreadsheet Components
 How can I create an MS Excel compatible spreadsheet file from my app without running Excel?
 How to read data from XLS, XLSX or CSV files without the need for MS Excel?
 How to programatically manipulate the contents of an MS Excel spreadsheet
 Can I use a spreadsheet to perform calculations and get the results back in my application?

C/C++ Spreadsheet Components by FarPoint Technologies, Inc.

Spread V8.0

Use FarPoint's Spread to easily incorporate advanced grid and high-level spreadsheet features into your applications. You get unmatched flexibility at the cell level for maximum control over the display and entry of the data, plenty of events to respond to user changes and an impressive feature list for everything in between; including import/export capabilities, enhanced printing, 14 cell types, formulas, plus many more features you'd expect from the market-leading component.

C/C++ Spreadsheet Components by Libexcel

Libexcel library for C++ V1.2.2

Write Excel Spreadsheets with rich formatting.

C/C++ Spreadsheet Components by SM Software

TXLSFile V4.0 -  TXLSFile is a Delphi library for reading and writing of Microsoft Excel XLS files. It is based on direct reading and writing of files, and works without OLE Automation with Microsoft Excel. VB and C++ developers may use OLE XLSFile COM objects library.