LaTeX

• Rotate even pages -- A bash script to rotate the even pages of a document. Can be modified to do odd pages. I found this script here.

• tabmac—A macro for typesetting Young tableaux, more flexible than youngtab. According to the file, it's incomplete, but I've found it very useful.

• By default, LaTeX will only allow a matrix to have at most 10 columns. This can be changed with the command \setcounter{MaxMatrixCols}{n} where n is any number you want.
• One approach to left exponents is to use the macro \newcommand{\leftexp}[2]{{\vphantom{#2}}^{#1}{#2}} so that \leftexp{a}{b} produces b with a as its exponent on the left. The \vphantom is to match the height of the argument. Replace the ^ with _ for left subscripts. You can also combine them: unfortunately, this solution breaks down if you want left exponents and left subscripts, since they will left-align on an invisible object instead of right-aligning.
• When you want to write "f: X->Y", it's best to use f \colon X \to Y because the command \colon produces different spacing from just using the character :