This downloads all variants of a Google Web Font. Please be sure that the font in question uses a license that allows this.

getwebfont.sh

#!/bin/bash

family=`echo "$1"|tr ' ' '+'`
filename=`echo "$1"|sed 's/ //g'`
weight=$2
subset=$3

if [ "$weight" != "" ]; then
	family="$family:$weight"
	filename="$filename-$weight"
fi

if [ "$subset" != "" ]; then
	family="$family&subset=$subset"
fi

function getfont () {
	curl -s -A "$1" "http://fonts.googleapis.com/css?family=$family"| \
	grep -io '\<http://[-+%:,/\._?&=#a-z0-9]*'|sort -u| \
	while read url; do
		mime=`curl -s -I "$url"|grep -io '^Content-Type:.*'|sed 's/Content-Type:\s*\([^;]*\)\(;.*\)\?\s*$/\1/I'|tr -d '\r'`
		case "$mime" in
			font/eot)
				ext="eot"
				;;

			font/woff)
				ext="woff"
				;;

			font/ttf)
				ext="ttf"
				;;

			image/svg+xml)
				ext="svg"
				;;

			*)
				ext="bin"
				;;
		esac
		echo "downloading $filename.$ext"
		curl -s "$url" -o "$filename.$ext" || exit 1
	done
}

getfont "Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 7.1; Trident/5.0)"
getfont "Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_1 like Mac OS X; en-us) AppleWebKit/532.9 (KHTML, like Gecko) Version/4.0.5 Mobile/8B117 Safari/6531.22.7"
getfont "Mozilla/6.0 (Windows NT 6.2; WOW64; rv:16.0.1) Gecko/20121011 Firefox/16.0.1"

Usage:

./getwebfont.sh font-family [font-weight] [subset]

Example:

$ ./getwebfont.sh "Open Sans" 400
downloading OpenSans-400.eot
downloading OpenSans-400.woff
downloading OpenSans-400.svg
downloading OpenSans-400.ttf