Whats a good 3d mmorpg maker that's free and easy to use?

It sounds like you want to program a 3D world using Machinima; I have very limited knowledge of this stuff, but I know my college uses it to teach first-time programmers about basic concepts in 3D modeling…if you wiki Machinina, you’ll see that it was used to develop WoW;

As far as using a virtual environment, I’d also consider exploring Second Life.

there probably isnt one for an mmo..best exploring your concept using something like microsofts XNA. Its hard near impossible to make one without hugs resources in network and a higher level game engine