These sites have information that can help you with almost any math topic.
1. Wolfram Alpha: Computational Knowledge Engine
http://www.wolframalpha.com/ This site offers information on any math topic. You just type in what you want to know or learn about and it gives you the information. A great resource.
2. MathTV – Videos By Topic
http://www.mathtv.com/videos_by_topic This site has math videos on how to solve problems about basic math, algebra, geometry and beyond. It is organized by topics. There is a Spanish version too
3. Math is Fun – Maths Resources.
http://www.mathsisfun.com/index.htm This site is arranged by both grade level and topic. It has information on the topics, games, puzzles, an illustrated math dictionary and practice worksheets.