You can also use the following bash/zsh function to quickly set the current default profile (requires ruby):

    function aws_switch () {
        local env="$1"
        local region="$2"
        export AWS_DEFAULT_PROFILE="$env"
        export AWS_ENV="$env"
        export KITCHEN_ENV="$env"
        export AWS_ACCESS_KEY_ID=$(/usr/bin/env ruby -e "require 'inifile'; puts IniFile.load(File.join(File.expand_path('~'), '.aws', 'credentials'))[ENV['AWS_DEFAULT_PROFILE']]['aws_access_key_id']")
        export AWS_SECRET_ACCESS_KEY=$(/usr/bin/env ruby -e "require 'inifile'; puts IniFile.load(File.join(File.expand_path('~'), '.aws', 'credentials'))[ENV['AWS_DEFAULT_PROFILE']]['aws_secret_access_key']")
        if [ -z "$region" ]
        then
            export AWS_REGION=$(/usr/bin/env ruby -e "require 'inifile'; puts IniFile.load(File.join(File.expand_path('~'), '.aws', 'config'))['profile ' + ENV['AWS_DEFAULT_PROFILE']]['region']")
        else
            export AWS_REGION="$region"
        fi
        export AWS_DEFAULT_REGION=$AWS_REGION
    }