The Khan Academy is a non-profit providing free educational material including short video lectures and practice exercises in mathematics as well as many other subject areas. A truly fantastic resource for any student. There is so much here, especially in maths, that it can sometimes be difficult to find the specific material you need. If that’s an issue, let me know, and I’ll point you in the right direction.
Exam Solutions is a UK-based site and so focuses on the UK mathematics curriculum. While the excellent videos are a great resource for any student, the site is particularly useful to students in NZ who are studying toward the Cambridge exams. A large collection of video tutorials cover most areas of the curriculum as well as example worked answers to past exam questions.