Up until my disastrous, nonexistent seventh grade, we used A Beka Books curriculum for everything. I really liked their textbooks and workbooks, which contributed to my current obsession with the same.
However, they taught me that all subjects are taught a certain way. For example, I never truly saw the use of labs, dissection, experiments, and observation to learn science. Even my nature-loving dad never really taught me through these techniques. Everything I ever learned about science, I learned first from these textbooks, and then later from documentaries. With extremely rare exceptions, I learned about ‘school subjects’ through books and worksheets.
As a result, whenever I’ve constructed a curriculum in the past, I tried to give every subject a similar learning technique. Keep in mind that in all things, I try to learn for free. Of course, at first I started with textbooks. Then I looked for podcasts and audiobooks. I’ve dabbled in online courses and interactive apps. In other words, the solution is a mixed bag of resources.
The number of educational websites has exploded. You can find instructions for any task and an explanation for every obscure concept. Best of all, just about all of it is available for free, though you might have to register for a free account on some websites.
Google every subject you want to learn and look for well-built, trustworthy websites. WannaLearn is a great index through which to find helpful material. Lifehacker has a great guide to online learning.
There are loads of free or cheap smartphone and tablet apps designed around teaching certain subjects, such as foreign languages, math, and vocabulary. There are also great web-apps like FreeRice, which behave like an interactive game.
YouTube is full of helpful folks who like to teach about various subjects. The guys at Crash Course have funny, basic lessons to take you through biology and world history. PBS.org lets you watch full-length, professional documentaries for free.
Whether you buy cheap, used textbooks, pirate them in PDF form, or buy the ebooks for phone-reading, you can generally find a book about anything you’d like to learn. However, don’t choose a book by its title and cover and immediately assume it’ll work as your sole resource for that subject; I often get into the first chapter of a book only to discover that it’s poorly written, uninteresting, is too basic or advanced, or has nothing to do with what I really want to learn about the subject. So be ready to shop around.
If you like listening to something while driving, doing chores, or working, audiobooks and ongoing podcasts are a great way to get in some learning. You can find a podcast about almost anything, from the history of Rome to basic economics.
Message boards, sub-reddits, and friends can be a good way to find and share resources and trade explanations of complicated topics.