National Council of Teachers of Mathematics - This site is the go-to resource for mathematics teachers. It includes a variety of lesson plans, professional development resources, and research
Wolfram Alpha -This computational engine can solve many types of mathematical problems. It's a great tool for checking work and understanding the steps in complex problems
MathOverflow -A question and answer site for professional mathematicians
It is important to evaluate your sources before using them in an assignment. Does your professor require you to have scholarly sources or the most recent research? This is where the limiters in QuickSearch can help you.