Cool software

Office / Documents

Libre Office - Office Suite (open source)

Graphics / Audio / Video

Gimp - Extendable rasterization graphics editor (open source)

Blender - 3D modeling / animation (open source)

Programming / Text

SublimeText - Really nice, extendable text editor (commercial)

Atom - Hackable text editor by GitHub (open souce)

Self-hosted clouds

Nextcloud - File cloud [PHP, MySQL] (open source)

ownCloud - File cloud with extensions for calendar, contacts etc. [PHP, MySQL] (open source)

cozyCloud - File cloud with extensions for calendar, contacts etc. [nodejs] (open source)