The CSV to XLS program allows you to convert your csv (comma-separated value) files to Excel format. Generally, you can use any delimiter, such as TAB, semicolon etc. The converter supports both 95-2003 MS Office format and 2007-2010 format too.
Since many programs can save data in CSV format then this programs can help you transfer these data to Excel files. You can run the program in a batch mode using command line interface. Besides, it includes a DLL which you can use from your own application.