Somehow, i forgot to post about the free content offered by CII-Shiksha, the organisation i am involved with. Since CII-Shiksha is a non-profit and so the content is free for anybody to download, use, redistribute, etc. There are 32 lessons / modules from Mathematics, Physics, Chemistry, Biology and Geography. The uniqueness of the content lies in the fact that it contains a good mixture of various multimedia components, is self-driven, etc. The idea behind creating the content was to develop some quality content that could be made available to rural schools and children in India, who either do not have quality teachers or no teachers at all. Every module has exercises, quizzes, an animated character guiding the learner, summary, etc. The modules are created to provide a conceptual understanding of the topic. The content could be downloaded from free Shiksha portal, www.eshikshaindia.in/downloadform.html
give it a try and do give feedback.
best of exploring !