I find that having caps lock mapped to control is also as conveninent as having it mapped to escape. So I use xcape to have left control act as escape if tapped by itself or as control if used in a chord (ctrl-a). You will of course need to map caps lock to control beforehand though:Check http://geekhack.org/index.php?topic=41685.0 and http://www.emacswiki.org/emacs/MovingTheCtrlKey for other systems.