On my home PC, I have a 'normal' copy of Firefox, then I install Portable Firefox on every other machine I need to sync. I then zip up my profile directory (see Daniel's comment above for location) and upload it to a free online file hosting service like DivShare or put it on a USB flash drive or similar. I then copy this profile into the Portable Firefox profiles directory on every other machine.
This seems like a pain to do on a frequent basis, but by using the Foxmarks and Google Browser Sync it automatically syncs bookmarks, history, cookies, saved passwords and even saved tabs/windows without having to replace the profile. So, in actual practice, I find I only have to replace the Portable Firefox profile when I make major changes to my main Firefox, such as new extensions or changing browser settings. Hope this helps!




