With older students in mind including those about to enter higher education, there are many free resources available to support students in their study of Mathematics. Note that a new blog aimed at students is now available.
There are many sources of excellent notes online, a page on Mathematics for Students – Notes has an excellent collection.
I would advise students of any subject to learn to use WolframAlpha. Suppose you wish to do some revision on techniques for differentiation for example – ask WolframAlpha to differentiate x2sinx, and the derivative will be returned with possible working available if ‘Show steps’ is selected. (Further Calculus examples). WolframAlpha provides an excellent way to check your work.
WolframAlpha can be used for vocabulary, for example, try typing ‘plus’ into WolframAlpha.
Note that WolframAlpha has assumed plus is a character but you can choose to refer to a mathematical definition or a word (or an internet architecture topic). Choosing wordwill not only give definitions but a wealth of other information that you would not find in a dictionary such as the first known use of the word, frequency of use, rhyming words and much more!
WolframAlpha Widgets are mini applications built on Wolfram Alpha queries. You can share them in several ways – Facebook and Twitter for example or embed them in a blog or website. Either use a widget from the growing gallery (note the categories on the right) – see Mathematics here or create your own.