Courses are suitable for people who prefer structured learning about a specific topic, but keep in mind they take time and commitment to complete. This is only a small sampling of the kinds of free courses you can find online. Search on Coursera, or EdX for a more exhaustive list.
Note: Coursera courses are free but certificates must be paid for. Specializations (a collection of related courses) are not free.
The Science of the Solar System– Caltech
Journey of the Universe- A Story for Our Times (specialization)- Yale University
Origins- Formation of the Universe, Solar System, Earth and Life– University of Copenhagen
Introduction to Thermodynamics: Transferring Energy from Here to There– University of Michigan
From the Big Bang to Dark Energy– University of Tokyo
Astronomy: Exploring Time and Space– University of Arizona
Mechanics: Motion, Forces, Energy and Gravity, from Particles to Planets– The University of New South Wales
MIT OCW is another great, classic resource. They have courses on everything from physics to history.