How to include the working directory in your UNIX prompt

I can never remember how to do this since it varies with the shell and its always hard to find by RTFMing.
so without further ado..

ksh

export PS1='$PWD>'

bash

PS1='\w>'

zsh

export PS1='%~>'

tcsh

set prompt='%~>'

csh

alias cd 'chdir \!* && set prompt="`pwd`>"'

sh

cd() { chdir $* ; PS1="`pwd` >"; }