Will Humans Return to the Moon?

Could NASA use the moon as a sort of checkpoint to reach Mars? How soon will we send spacecraft?

Unlike Mars, there are some very useful things we could do on the moon if we had the capability and financing. Whether the moon will be used as a stepping stone has been discussed in the past, but that part has an uncertain future.
The moon itself is very reachable. We’ve done it before! One very useful thing we could do on the moon would be to position a huge parabolic telescope nestled in a crater, preferably on the far side facing into deep space so Earth wouldn’t be in the way of the view.
Such a device would be of incredible importance to scientists.
To build it is another thing altogether. Can you imagine? Bringing all that stuff up there, dropping it off, then have either robotic machines or humans assemble it, and because it being on the far side of the moon, communication with Earth would be an interesting problem to solve as well.
There are a number of really useful things we can do on the Moon. When and if it will ever happen will have to be seen.