AppendColumns, AppendRows, and BlockMatrix are available using the Mathematica kernel functions Join and ArrayFlatten.
TakeRows, TakeColumns, TakeMatrix, and SubMatrix are available using the Mathematica kernel function Take.
HankelMatrix and HilbertMatrix are available as the kernel functions HankelMatrix and HilbertMatrix.
The functionality of ZeroMatrix can be obtained using the new kernel function ConstantArray.
The functionality of PolarDecomposition can be obtained using the enhanced Mathematica kernel function SingularValueDecomposition.
MatrixPlot is now available as the kernel function MatrixPlot.
These functions were available in previous versions of Mathematica and are now available on the web at library.wolfram.com/infocenter/MathSource/6770: