http://www.wolframalpha.com/
Not only helpful with math, but that's what I use it for. You can type in pretty much any kind of problem and it will solve it, or at least give you helpful information that will lead to the solution. I'm taking an online college algebra class at the moment and I could probably pass the class using nothing but this.
EDIT: This is also really helpful, often even more helpful than WolframAlpha:
http://webgraphing.com/
You need an account to get full benefits, but accounts are free, and you can just use this one I already made:
User: UHME
Pass: UHME
Not only helpful with math, but that's what I use it for. You can type in pretty much any kind of problem and it will solve it, or at least give you helpful information that will lead to the solution. I'm taking an online college algebra class at the moment and I could probably pass the class using nothing but this.
EDIT: This is also really helpful, often even more helpful than WolframAlpha:
http://webgraphing.com/
You need an account to get full benefits, but accounts are free, and you can just use this one I already made:
User: UHME
Pass: UHME









