Timeful
link: https://timeful.app/
Coordinate group meetings with a shared calendar to match availability.
I Love PDF
link: https://www.ilovepdf.com/
Pretty much all the tools that you could need to handle pdf files
Merge, split, edit, transform, sign etc.
Jitsi
link: https://meet.jit.si/
Open source video conference and meeting software
One time secret
link: https://onetimesecret.com/
Encrypt messages for easy sharing of compromising data with a one time use link
Cyber Cheff
link: https://gchq.github.io/CyberChef/
Great compilation of online tools for encrypting, decrypting, and transforming different formats, as well as forensic tools.
Usefull for CTF competitions and other cybersecurity activities.
OpenCut (beta)
link: https://opencut.app/
Opensource online video editor
Graphite
link: https://graphite.rs/
Opensource vector and raster graphics editor
Photopea
link: https://www.photopea.com/
Online photo editing software, with support for a variety of formats including .pds