Rich asks:

<<
Does anyone know of a compendium of matrix arithmetic?
I'm imagining a collection of numerical & simple algebraic
facts about matrices-- things like the determinant of a
Vandermonde matrix, or the inverse of a finite section
of Pascal's Triangle.
>>

This is probably more advanced than you're looking for, but a wonderful book that's jam-packed with matrix facts but whose emphasis is on good robust algorithms for various matrix computations is by Golub & Van Loan, now in its nth edition where n >= 3.

--Dan