Below is a list of some online resources that I find useful. I also provided a short description of each website and the features that they have to offer. Please keep in mind if you cannot find the answers you are looking for on any of these sites... I am also a resource!
Although the layout of this website is not as user friendly as some of the other resources listed here, S.O.S. math provides explanations and examples on a wide variety of math topics. Several topics have example problems and well explained solutions to guide you through the problem solving process. The website also has a feature called CyberExams that provides multiple choice quizzes for practice.
This is a well designed website with clearly defined access to the traditional high school math subjects. Each topic has lessons, explanations, and examples that are easy to find and follow. Several topics also have supplemental video lessons. Math Planet also provides example SAT and ACT math problems with videos that explain the correct answer and downloadable answer keys.
Khan Academy is probably the most well known online math resource. Once you get to the homepage, click the "start learning now" tab and you will be prompted to sign in. It is completely free and only takes a minute or so. You can then search topics or select math by subject. There are so many useful and easy to find video lessons, it is no wonder this is a favorite.
Patrick JMT is very similar to Khan Academy. JMT stands for "Just Math Tutorials" so it has several video tutorials. It is a simpler version of Khan Academy and the amount and layout of topics can be a little overwhelming, but there is still a lot of useful information on here.
This website was created by a professor at Lamar University so it was designed with college level mathematics in mind. That being said, there are notes on subjects ranging from Algebra to Calculus. This is a website that I personally used a lot in college because it has easy to follow notes and examples. There are also practice problems for students to solve that show step-by-step solutions which can be revealed one at a time. This website also provides "cheat sheets" for algebra, trigonometry, and calculus topics with facts and formulas.