gemcutter master $ gem fetch rails
Downloaded rails-2.3.4

gemcutter master $ gem unpack rails-2.3.4.gem --target=/tmp
Unpacked gem: '/tmp/rails-2.3.4'

gemcutter master $ ls /tmp/rails-2.3.4
CHANGELOG    README    bin      configs     doc           fresh_rakefile  helpers  lib
MIT-LICENSE  Rakefile  builtin  dispatches  environments  guides          html