The Arduino pin names are silkscreened right on the board, but sometimes you must know the corresponding ATMega168 pin name. I printed out The Fine Manual and penciled in the Arduino names, but that’s getting smudgy.
Herewith, the ATmega168 pinout with neatly printed Arduino pin names.
[Update:Turns out there's an Official Version.]
Sometimes, you also must know the relation between hardware Timers and PWM output pins: