Wow I cant believe I have never heard of this site before. Hippocampus is an access port to lots of online content (through something called the National Repository of Online Courses) Lots of content resources for different classes. For Algebra there are about 100 interactive lessons in English and Spanish. You can browse lessons by topic or by page number of different textbooks.
The license is strange - students and "individual teachers" can use the site at no charge but "educational institutions" need to pay a fee. There is no explanation of what the difference is (last time I checked most teachers worked at educational institutions).
