Roll20 - Roll20 is a suite of easy-to-use digital tools that expand pen-and-paper gameplay.
MasterScreen - MasterScreen is the ultimate set of tools for running tabletop or online roleplay campaigns and managing intricate fictional worlds. Free for everyone.
D&D Beyond - Official online toolset for Dungeons & Dragons tabletop gaming
Foundry Virtual Tabletop - A self-hosted, modern, and developer-friendly roleplaying platform.
dmtools - desktop tool for dungeon masters by a dungeon master
Beyond Tabletop - Beyond Tabletop is a set of tools for RPG players with easy-to-use online character sheets and maps.