$\newcommand{\identity}{\mathrm{id}} \newcommand{\notdivide}{{\not{\mid}}} \newcommand{\notsubset}{\not\subset} \newcommand{\lcm}{\operatorname{lcm}} \newcommand{\gf}{\operatorname{GF}} \newcommand{\inn}{\operatorname{Inn}} \newcommand{\aut}{\operatorname{Aut}} \newcommand{\Hom}{\operatorname{Hom}} \newcommand{\cis}{\operatorname{cis}} \newcommand{\chr}{\operatorname{char}} \newcommand{\Null}{\operatorname{Null}} \newcommand{\lt}{<} \newcommand{\gt}{>} \newcommand{\amp}{&}$
1. VectorEquation: cdf/VectorEquation/VectorEquation.cdf Visualize linear combinations of two vectors in $\mathbb{R}^2$ and use them to solve a linear system.
2. CoordinateExplorer: cdf/CoordinateExplorer/CoordinateExplorer.cdf Visualize coordinate systems determined by two different choices of basis for $\mathbb{R}^2\text{.}$
3. LinearSolver: cdf/LinearSolver/LinearSolver.cdf (Popular) Visualize a $2\times 2$ matrix as a transformation from domain to codomain, and use the result to visualize what solving its associated linear system looks like.