True confession: A very strong argument can be made that the only reason I homeschool is to have an excuse to a.) buy books and b.) to pretend like I'm back in grad school doing research.
I love doing research. I love the process of discovery, the serendipity of finding a wonderful book on the library shelves when I was looking for something else. I love making new connections between seemingly unrelated topics. I love Google though there are times when I clearly need to learn how to refine my search parameters. I love that Amazon has reader reviews and the lists other readers create. I like the simple act of scribbling down titles and ideas, I even love the look of my notebook pages when they are filled with messy lists and tiny sideways commentary about books or library call numbers. I love how much I have learned by simply researching topics for homeschooling.
I also love discussions on the WTM high school discussion board about books that teens have loved or that moms recommend. Over the years I've jotted down several pages of titles, and while I have used only a fraction of them, it has been an excellent starting point for planning a reading list or a course.
The research part is easy. Start with a germ of an idea and do a Google search. Throw in the words "lesson plans" to get a different subset of hits. Go to Amazon and search for books on the subject, read the publisher's description, read the reader reviews, then click on the related titles they suggest. Look for documentaries. Then search your local library to see if they have any of the titles you like. Head to the library and browse the section where books or DVDs on this topic are shelved and look for other titles that you missed in your searches. Sit down right there in front of the shelf and flip through all the books on that topic. Do the same thing at your local book store.
Deciding what is worthwhile isn't always so easy. There are many insipid reader reviews on Amazon, but there are also thoughtful reviews about the merits or shortcomings of a title. I only bookmark a tiny fraction of Google hits. I look for sites that have really useful activities, or that have nice back ground articles. You have to trust your judgement, something that will become more refined as you gain experience in teaching a class or developing a course for your kids.
I do this kind of research for every course and class I have ever planned, and I don't find it all that time consuming or overwhelming. It does require some quiet time, but since I enjoy it, I'm happy to spend my free time googling and searching. Some of the wonderful things I stumbled upon include a wonderful series of NASA lesson plans on Newton's 3 laws of motion which I have used in co-op settings and just with my kids. I found playground physics activities I did with an elementary science co-op and I found high school level biology projects for my 10th grader. I ordered a cinematography book from Amazon for my oldest ds based on reviews, and learned after it arrived that it is considered "The Bible" of cinematography titles.
The funniest part is that between my research and Christmas shopping, Amazon has no clue what my real interests are. The recommended titles that show up when I open the main page are laughable -- today I am greeted with a list of Lego books and sci fi titles, several editions of Arthur Conan Doyle's Lost World and a smattering of Disney trivia titles. They'll never know the real me!