I have not used it myself, but I have heard positive things about World Anvil from other people. It seems to have tools both for worldbuilding in general, and organisational tools for campaigns and GMing.
Several of the campaigns I'm in have used/are using Trello as an organisational tool to keep track of characters, locations, NPCs and plot-hooks - it's a pretty handy way of keeping track of what's been happening, and sharing information with players.