While many of us have become pampered by DND Beyond's rulebook integration, Beyond Tabletop brings us back to our basics. By removing the integrated rulebooks they allow for every feature to be homebrewed and managed how you and your DM desire. In my findings it is the best tool out there as far as capturing the feel of pen and paper while also giving the versatility and ease of access of the internet.
Roll20 - Roll20 is a suite of easy-to-use digital tools that expand pen-and-paper gameplay.
Codezero - Collaborative Local Microservices Development
Astral Tabletop - Create, host, and manage your tabletop role-playing games — online or in person
LeadMD - LeadMD is the revenue performance consultancy that cuts through the BS by making your vision actionable and your outcomes measureable
Fantasy Grounds - Fantasy Grounds is a virtual tabletop to help facilitate play of tabletop-style role-playing games...
Sirius - An open-source clone of Siri from UMICH