diagrams.net: Webapp for creating clean, custom diagrams.

overleaf.com: Online, no-fuss LaTeX editor with collaboration.

discord.com: Community building and management with voice, video, text.

rstudio.cloud: R data analysis and kit, hosted online for free.

github.com: Version control for any and all code, hosted online.

simplenote.com: Simple, fast, cross-platform notetaking.

atom.io: Highly customizable and extensible text editor.