Where can you find over 100 free high quality unit studies? Boy Scouts!
The Boy Scouts of America (BSA) program offers great merit badge materials to its Scouts, which my older sons used on their way to achieving their Eagle Scout ranks. Completing merit badge requirements was often a great addition to their study of science, history, culture, government, business, and technology, and they also learned some great life skills for staying fit and healthy, managing money, and dealing with emergencies.
Participation in BSA was rewarding for our family, but even if your kids aren't Scouts (or boys!), you can use the merit badge program instead of curriculum to give your kids a great introduction to many interesting topics. One thing BSA understands is active learning, and many of the merit badge requirements are project-type activities with a meaningful hands-on component. However, many of the merit badges also have reading, writing, and research components, thus reinforcing academic skills we want our kids to practice.
Merit badges are completely presented in over 130 merit badge pamphlets, which you can buy at your local Scouts Shop or order online from BSA for $4.99 each.
However, the detailed requirements for each merit badge -- minus the informative text that is in the merit badge pamphlets you can purchase -- are available free online [ED: this link is temporarily unavailable but the same content is available here], and combined with the library and internet resources, will provide plenty of homeschool learning activities on their own.
Among the unit studies, uhhhh, I mean, merit badges that cover typical specific "school-type" subjects: engineering, energy, digital technology, mammal study, reptile and amphibian study, robotics, chemistry, astronomy, bird study, insect study, archaeology, reading, and many more.
Among the merit badges that cover outdoor adventuring and management: forestry, camping, hiking, kayaking, swimming, climbing, cycling, fly fishing, environmental science, backpacking, archery and more.
Those that cover life skills include personal fitness, personal management, cooking, family life, emergency preparedness, lifesaving, and citizenship.
Along with several other types of merit badges, there are even merit badges offered that would be useful in business -- entrepreneurship, salesmanship, communication, public speaking, and American business.
Clearly, this is a rich resource for homeschooling families -- and that's before mentioning the quirkier merit badges your kids might love: farm mechanics, welding, aviation, movie-making, geocaching, radio, and sculpture.
There is a complete online list of merit badges [ED: this link is temporarily unavailable but the same content is available here], and clicking on each individual merit badge takes you to its own page listing requirements, resources you can use to meet the requirements, and external links related to the topic.
Take the Bird Study merit badge [ED: this link is temporarily unavailable but the same content is available here], for example. The merit badge requirements include discovering how birds can indicate the quality of an environment, sketching and labeling birds and their anatomy, learning how to use binoculars, learning to use a field guide (including range maps), preparing a field notebook and identifying at least 20 bird species, understanding the function of bird songs and identifying some birds by their song alone, participating in a bird count, and building a bird feeder, bird house, or bird bath according to particular species' needs.
The resources and links that are available alongside the Bird Study requirements include some helpful online videos and articles -- how to use and care for binoculars, the BirdJam website that plays bird songs and helps you learn to identify birds, a link to Audubon's Christmas bird count information, and a link to the beautiful and informative Cornell Ornithology Lab. The Cornell Ornithology Lab site is incredibly rich, including an online guide to identifying birds and a wonderful collection of live bird cams.
(I did find BSA has the same problem the rest of us do -- there are some dead links here and there. However, those few gaps are easily filled in with a little googling).
All this combines to make a pretty good introductory to intermediate bird study, and it could be part of a larger biology or environmental science study as well.
The other merit badges work the same way -- requirements plus great resources, presented in a concise way.
There are often even links for how to host a "merit badge day" to help Scouts achieve as many of the requirements for a specific badge in one day as possible. You could easily adapt this model for a group of homeschooling friends or your co-op.
BSA's merit badge program can definitely help you "be prepared" with great learning activities for your kids.