OBS
The Open Broadcast Software Project or OBS is a free and open-source software that is used for video recording and live streaming. Since it is open source, there are a lot of available plugins to extend functionality and there is a very active modding community. Originally only available via a plugin, OBS now has integrated Virtual Camera functionality. This allows you to take your OBS composition and turn it into a camera feed that can be used anywhere where a regular camera input would be taken (Zoom etc). This function opens up a wide range of streaming and remote working possibilities without requiring expensive software or hardware. OBS has a highly customizable interface but because of this can seem a little intimidating to new users.
Chroma keying can be done directly in OBS and can be pretty clean when paired with quality lighting. The combination of OBS, chroma-keying, and vdo.ninja can be quite powerful for long-distance collaboration where the desired outcome is for multiple feeds to exist in the same virtual space.
OBS has plugins that add functionality for NDI and Spout
COST: Free
Projects that used OBS: