1) Decided to consider making my "Mathematics: It Is Not Just Calculus" book into an open-source book, hosted on sage.math.washington.edu and with exercises written in Sage.
2) Figured out that LQUP, Bunch and Hopcroft, and LSP are all actually the same.
3) Extended Rose's MinDegree algorithm, for Cholesky factorization of sparse symmetric positive definite complex-valued matrices via graph theory to matrices that are rectangular, not symmetric, not PSD, over any non-tiny field, using di-graphs. And it goes to RREF, so can be used in Groebner Bases.
4) Watched Robert Miller code that.
5) Began writing a paper (11 pages so far) Bard-Miller'08.
6) Lost my "Sage" and "Python" virginity...
7) ..by writing a Nash-Equilibrium finding library of functions for game theory. Rock, Scissors, Paper and RSP+Bomb are built in. It wasn't painless but that just makes it more fun. Painless is pointless.
8) Saw my dissertation referred to dozens of times.
9) Watched M4RI and M4RM get improved, which is an ego trip!
10) Rediscovered the sandwich, I had forgotten that they can be non-trivial.