Power Point Presentations are a great resource for studying. Do you know you can find free power points with Google by typing in a concept for keywords and ".ppt" into the search?
For example if you want to find Power Point Presentations about weather I would type in
into google search.
Or you can look through a great directory form Pete's Power Point Station
I have found a good section here for Weather and here for Fractions that you can download, open, view, print, and study from.