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:
#!/bin/sh
here="`dirname \"$0\"`"
echo "Starting Thunderbird from '$here'."
echo "Wait a while before Thunderbird start."
cd "$here/app/Thunderbird.app/Contents/MacOS/"
./thunderbird-bin -profile "$here/profile"
echo "Done!"
echo "When finish, quit Terminal.app before eject your portable device."
English version is available here:
http://www.freesmug.org/portableapps/thunderbird/
I hope in some more expert users help me to relese also other OS X portable applications like OpenOffice, Nvu, NeoOffice, Abiword, Adium...