SimpleXlsxWriter

This library represents XLSX files writer for Microsoft Excel 2007 and above.

The main feature of this library is that it uses C++ standard file streams. On the one hand it results in almost unnoticeable memory and CPU resources consumption while processing (that may be very useful at saving a large data arrays), but on the other hand it makes unfeasible to edit data that were written.
Hence, if using this library the structure of the future report should be known enough.

The library is written in C++ with using STL functionality and based on the ZIP library (included), which has a free license:
http://www.codeproject.com/Articles/7530/Zip-Utils-clean-elegant-simple-C-Win32

This library is distributed under the terms of the zlib license:
http://www.zlib.net/zlib_license.html