Another useful one is !* which give you all of the arguments from the previous command:
$ ls foo bar bing
foo bar bing
$ echo !*
echo foo bar bing
foo bar bing

You can also get the Nth argument with !:N
$ ls foo bar bing
foo bar bing
$ echo !:2
echo bar
bar

You can combine this with matching the most recent line that begins with a particular string:
$ echo !ls:1
echo foo
foo

$ echo !ls:*
echo foo bar bing
foo bar bing

$ echo !ls:0
echo ls
ls

Ok, the last one seems kinda silly, but it could be useful if you have several commands that start with the same string and you want to know which one you did most recently.

$ foocreate
$ foostart
$ foostop
$ foostart

$ echo !foo:0
echo foostart
foostart

Keith

ESC-_

ls /etc/passwd
cat[ESC-_] -> cat /etc/passwd