Desmos

The best online and mobile app for graphing with technology.
 

ProjectEuler.net

Challenging Mathematical / Computer Programming Problems

LOOM

Record your screen and camera image with audio for quick videos, reviews, & screencasts.

WordClouds.com

Create free word clouds. A cluster of words arranged to create a shape/picture.

Symbolab

Online Equation solver that is a great tool to check your work, and get step by step solutions.

Past Contests

Problems, solutions and results dating back to 1998. Both Math and Computer Science

HackerRank

Coding challenges to demonstrate problem solving skills. Maybe even get noticed.