PHPExcel
Decided to find out if there were any free libraries that would allow you to create Excel files from scratch. Idea being that you can call this from PHP and create a spreadsheet from a website. Not a new idea but anyway. Found PHPExcel v1.7.0 and got it installed and running very quickly. Great piece of work. I will likely use it at some point in some project or other. Oh, it writes Excel 2007 format too.