Every photographer should have a collection of projects. A project can be a specific limited thing, such as an exhibition, or it can be an ongoing thing, such as taking photos of green cars.
Projects are not necessarily attempts to push the art forward or make money; they may simply be a means of inspiration, of pushing oneself to keep taking photos even at times of low motivation.
I have many such projects. This list will start small, but hopefully will grow as I upload more to share.