Below are a list of sites that I have found useful for learning about science, math, and critical thinking.
Critical Thinking
Snopes - Snopes is one of the most comprehensive and up-to-date sites when trying to determine if an urban legend or news story is real of not.
What's the Harm? - Often when pseudoscience is talked brought up, someone will ask "what's the harm?" This site shows specific cases where harm was caused by believing in false ideas.