Apt

Includes handy things like

find which package contains empheq.sty with apt-file search empheq.sty

xmodmap

To remap the left and right arrow of Lacra's pointer to the down and right arrows, respectively, did
xmodmap -e "keycode 117 = Right" xmodmap -e "keycode 112 = Down" found the keycodes useing xev. This list of symbol names may be useful: [1]

tcpdump

tcpdump -i wlan0 -n -s 64000 -w http.dmp

Caltech

Pam Fong's math computing stuff: [2]