Resources: Online Learning Components for Holt/McDougal publications

Click on the subject and a state on this page:

http://www.classzone.com/cz/index.htm##

And it takes you to a list of books. Click one, and you get to the online support page for that book. Some of these are chock full of activities, animated lessons, links, tutorials (like on math topics), online worksheets, etc. While some of these activities are very book-dependent, others are linked to a specific piece of literature or knowledge you can access elsewhere (like in a "complete works of O. Henry" book you could find in a library or elsewhere online or a math concept).

And they're free.

And useful even if you don't own the books.