DroneDeploy is really easy, and has some added features like 3D point cloud models. You can sign up for a free account which will get you five "maps" per month, but I believe it's at a reduced resolution. I had fun playing with it. If you do it for a business you can buy a subscription which will get you some great bells and whistles, including NDVI mapping. I tried some other free options, but they were not easy by any means.