Worldbuilding & Campaign Management
World Anvil – Deep worldbuilding tool with timelines, maps, and campaign management.
https://www.worldanvil.com

Obsidian Portal – Campaign wiki and adventure log platform for organizing your game.
https://www.obsidianportal.com

Kanka.io – Modular platform for managing worlds, characters, events, and timelines.
https://kanka.io/en

LegendKeeper – Interactive maps and wiki-style campaign content organizer.
https://www.legendkeeper.com

Encounter Builders & Monster Tools
Kobold Fight Club – Encounter builder for 5e that calculates difficulty and XP.
https://koboldplus.club

D&D Beyond Encounter Builder – Official 5e encounter builder integrated with D&D Beyond content.
https://www.dndbeyond.com/encounter-builder

Tetra Cube Statblock Generator – Custom monster statblock generator and encounter design.
https://tetra-cube.com/dnd/dnd-statblock.html

Map Makers & Virtual Tabletops (VTTs)
Dungeon Scrawl – Fast and simple web-based dungeon map maker.
https://www.dungeonscrawl.com

Inkarnate – High-quality world and regional fantasy map creation tool.
https://inkarnate.com

Owlbear Rodeo – Lightweight and fast VTT for quick online D&D sessions.
https://www.owlbear.rodeo

Foundry VTT – Advanced, self-hosted VTT with community-created modules and automation.
https://foundryvtt.com

Generators (Names, NPCs, Loot, Dungeons, etc.)
Donjon – Comprehensive random generator for dungeons, names, loot, encounters, and more.
https://donjon.bin.sh/d20/

Fantasy Name Generators – Thousands of name generators for fantasy races, places, and items.
https://www.fantasynamegenerators.com

Chartopia – Community-driven collection of random roll tables and generators.
https://chartopia.d12dev.com

Rules, Statblocks & SRDs
5etools – Comprehensive rules compendium including classes, spells, monsters, and magic items.
https://5e.tools