Schmoop is a useful site for English and History students. It is focussed on the US but contains useful resources for both teachers and students.Shmoop
Shmoop Learning GuidesTeacher Resources
Cliff Notes and Spark Notes both have excellent study guides for many subjects and both have a large selection of excellent apps for mobile phones and other portable devices.
The ever reliable BBC has some amazing study guides available on their website Bitesize. They are designed to be quick and easy.
Teacher Tube have many useful videos on their site and you can search through a huge amount of topics to find what you need. the videos are usually created by teachers or other students. They are all free, you need to apply for a membership, which is also free.

The Khan Academy is an amazing site full of intensive videos teaching all sorts of subjects, particularly ones where students find concepts difficult, such as calculus etc. Salman Khan, its founder, argues that we could flip around the way that we teach by viewing the lectures at home and then the 'homework' in class where the teacher can help them. His TED talk explains more and it is also on his website on the home page.

Live Binders are a way of collecting the best of the web on a topic of your choice and then collating them into a 'binder'. You create tabs and add in the material that you would like to place on each page. These can then be shared, offered for collaboration and commented on. One good example is this one on e-books.

Another really useful site for study is Cite This For Me which creates a Harvard style reference for any papers students (or teachers) are writing. You simply put in the details and it generates the bibliography and references and you download it in Word format.