Open source

What does open source mean and why should you care about it?

Free as in free beer
Free as in freedom of speech
Vendor lock-in
Exchanging your data

Office Suite

LibreOffice is a free and open-source office suite, comprising of programs for word processing (Writer = [equivalent to] Word [in Microsoft Office]), the creation and editing of spreadsheets (Calc = Excel), slideshows (Impress = PowerPoint), diagrams and drawings (Draw), working with databases (Base = Access), and composing mathematical formulae (Math = Formaula Editor). It, overall, has similar functionality to programs included in Microsoft Office and (from version 6.2) a similar user interface, aiming to make the transition from Microsoft Office easy. LibreOffice is available for all major platforms, including Microsoft Windows, macOS, and Linux. In addition, there is a LibreOffice Viewer for Android, as well as an online office suite LibreOffice Online.
LibreOffice uses OpenDocument file format (ODF; an international ISO/IEC standard) as its native format to save documents for all of its applications. It supports the file formats of most other major office suites, including Microsoft Office (however, the import from and the export to Microsoft office doesn't always work flawlessly; this is - in my opinion - more a problem of the Office file format because that, e.g., a Word document created on a Mac opens identically on a Windows PC can't be either taken for granted).

Software to create and manipulate graphics

Pixel-based

GIMP

Vector-bases

Inkscape

Statistical analyses

R
PSPP