Math-
BetterExplained: the website boasts, "Instead of memorizing procedures, learn why equations work. This site helps you overcome mental roadblocks and truly grasp new concepts."
Desmos: the website has an amazingly fast online calculator that can graph any imaginable function. It can also add sliders, do regressions, and plot whole data tables.
Research-
InstaGrok: the interactive search engine (is free for education) and generates subject-related videos, images & articles. It also helps to evaluate sources.
Productivity-
Unstuck: It is a digital life coach. It prompts you with questions about any given situation/ problem, and then gives you ideas how to get out of the predicament.