Homeschoolers can take advantage of the thousands of free printable worksheets available online.
The age of the Internet is the age of information. It is available free of cost. If you have the Internet and a printer, then you have "struck gold". You can find printable worksheets for any subject and topic needed when homeschooling. Here I will direct you to the best sites for each main subject.
I vote EdHelper's Math section the best for online free printables. It lists each grade up to grade six. There is also a section for middle school Math. Finally, it has Algebra I and II as well as Geometry printables. After you choose which grade or class you want, you will get a comprehensive list of the concepts taught. Each concept has several free printables to choose from. Just pick the one you want and print.
English Banana has my vote for best English printables. This site has over 1,000 printables concentrated on the subject of English. Click on free worksheets and then choose from Elementary, Intermediate, Advanced, Additional, Better English Lessons, and All. Every English concept taught in school is listed with a corresponding worksheet. Your child can work on letters, add past tense verbs to some stories, or practice handwriting. If you have never visited this site, then you definitely should.
Worksheets 4 Teachers lists printables by subject. The subjects include Anatomy, Earth Science, Biology, Physical Science, Chemistry, Space and Astronomy, and General Science. These worksheets aren't for the younger children, but you can get reproducibles at Enchanted Learning for younger children. My daughter is in the 4th grade and she likes the matching worksheets from this site. She just finished one on the plant life cycle.
History on the Net is a neat site that has plenty of history by subject matter. There is a page of subject choices. Click on the subject to get a long list of worksheets to print. Next to the title of each printable is a list of the skills that the worksheet covers. For example, solve a puzzle, complete a diagram, or answer questions pertaining to a lesson on the page. I like that there are so many ways to test a child's knowledge on the subject matter that you can pick the style that your child will respond to the best.