Great Math Sites
This is a fantastic site with videos and presentations on just about any topic/concept from elementary math to college-level courses
https://phet.colorado.edu/en/simulation/trig-tour for precalculus and calculus students. There is a great interactive applet that compares the unit circle with the linear sinx, cosx, tanx graphs, including special triangles, great visuals and degree/radian options.
https://phet.colorado.edu/en/simulations/category/by-level/high-school, for SCIENCE - Fun Physics Interactive Tools
http://www.regentsprep.org/Regents/math/algtrig/math-algtrig.htm Lessons, presentations and practice for Algebra 2 and Trig based on the New York end of-course tests.
Excellent site to calculate what you expect to get on the AP exam -- applicable to any AP test, not just math!
http://cnx.org/content/m18292/latest/ Great site - Found this information about matrices very helpful
http://www.intmath.com Great site for a variety of math concepts for middle and upper school with practice problems and respective solutions included
http://zonalandeducation.com/mmts/miscellaneousMath/intervalNotation/intervalNotation.html
Interval notation help
http://math123xyz.com/Nav/Pre-Algebra/index.php
Core standards with interactive games
http://www.learningwave.com/abmath/
Very fun!
http://cte.jhu.edu/techacademy/web/2000/heal/mathsites.htm
Listing of tons of math sites
http://en.wikipedia.org/wiki/Schr%C3%B6dinger's_cat
More for physics students, here is an explanation of co-existing states of reality in the form of the classic Quantum Physics experiment 'Schrodinger's Cat"