The vi survival guide
If, like mine, your colleagues are constantly moaning about vi when installing their machines, have them read this!
Print the essential commands shown below, stick them on top of the coffee machine and have your coworkers recite them before getting a coffee. After a week, they'll be ready to fix any Linux box with the stock tools, even when lost in the middle of a desert (I must admit I haven't tried the desert bit, but it should work).
toggles between insert and command mode
insert before cursor position
add at end of line
open (insert) a line after current line
delete current line
CTRL-F / CTRL-B
page forward / backward
quit and save
quit without saving
Other useful commands (partial list)
change word (end with ESC)
erase one character
delete 5 lines from current position
erase one word
copy current line to buffer (yank)
paste buffer after current line
display file information at bottom of screen
go to line 3
search forward for a regular expression
repeat forward search
repeat backwards search
replace word1 by word2 in the whole file with user confirmation.
replace word1 by word2 in current line with user confirmation.