Thin Firefox optimized for USB keychains

Dave sez, "Portable Firefox is a fully functional package of Firefox optimized for use on a USB key drive. It has some specially-selected optimizations to make it perform faster and extend the life of your USB key as well as a specialized launcher that will allow most of your favorite extensions to work as you switch computers."

Link

(Thanks, Dave!)

Update: Skippy mentions a version of Thunderbird (the Mozilla mailer), with GPG crypto protection also optimized for USB thumb-drives.