From the Terminal use the commands below.
Show
$ defaults write com.apple.finder AppleShowAllFiles TRUE
$ killall Finder
Hide
$ defaults write com.apple.finder AppleShowAllFiles FALSE
$ killall Finder
August 28, 2010
From the Terminal use the commands below.
$ defaults write com.apple.finder AppleShowAllFiles TRUE
$ killall Finder
$ defaults write com.apple.finder AppleShowAllFiles FALSE
$ killall Finder