Mathematical Association of America--The Mathematical Association of America is the largest professional society that focuses on mathematics accessible at the undergraduate level.
American Mathematical Society-- Association of professional mathematicians dedicated to furthering the interests of mathematical research, scholarship and education, and serving the national and international community through publications, meetings, advocacy and other programs
Wolfram Alpha--A computation engine that brings dynamic computations based on a vast collection of built-in data, algorithms, expert-level knowledge, and methods anywhere.