I wanted to major in physics when I went to college in 2013 (I'm 28 now), but had to drop out and have flushed out a lot of information. A lot of basic concepts are still there, but I'd need a lot of refreshers going back to like algebra lol. I'd love to get back in to studying in my free time, but I've completely forgotten how. Khan academy is great, but any other advice for reteaching and retaining would be awesome!
Your local public library is a great resource for this, if you have one. Most public libraries host classes, and even those that don't will know of community colleges that do. :)