From the experience of Portable Firefox OSX, I've packaged a Portable Thunderbird Mac OS X version using this script so you can launch it with a double click from any device:
echo "Starting Thunderbird from '$here'."
echo "Wait a while before Thunderbird start."
./thunderbird-bin -profile "$here/profile"
echo "When finish, quit Terminal.app before eject your portable device."
English version is available here:
I hope in some more expert users help me to relese also other OS X portable applications like OpenOffice, Nvu, NeoOffice, Abiword, Adium...