GnuPlot - Gnuplot is a portable command-line driven interactive data and function plotting utility.
Wondershare PDFelement - All-in-one PDF editor
GeoGebra - GeoGebra is free and multi-platform dynamic mathematics software for learning and teaching.
Foxit PhantomPDF - Edit PDF files with our feature-rich PDF Editor. Download Foxit PDF Editor to convert, sign, scan / OCR & more. A speedy PDF Editor alternative to Adobe Acrobat.
SciDaVis - SciDAVis is a free application for Scientific Data Analysis and Visualization.
Google Docs - Create a new document and edit with others at the same time -- from your computer, phone or tablet. Get stuff done with or without an internet connection. Use Docs to edit Word files. Free from Google.