Firefox - Full profile (addons, bookmarks, cookies)
This goes on the machine that you want the master profile on:
xcopy "%APPDATA%\Mozilla\Firefox" "\\server\FF\" /e /v /c /h /r /y
This goes on the machines that you want to pull the profile from:
xcopy "\\server\FF\" "%APPDATA%\Mozilla\Firefox" /e /v /c /h /r /y
Internet Explorer - Cookies and Bookmarks
This goes on the machine that you want the master profile on:
xcopy "%APPDATA%\Roaming\Microsoft\Windows\Cookies" "\\server\IE\cookies" /e /v /c /h /r /y
xcopy "%USERPROFILE%\Favorites" "\\server\IE\Bookmarks" /e /v /c /h /r /y
This goes on the machines that you want to pull the profile from:
xcopy "\\server\IE\" "%APPDATA%\Roaming\Microsoft\Windows\Cookies" /e /v /c /h /r /y
xcopy "\\server\IE\Bookmarks" "%USERPROFILE%\Favorites" /e /v /c /h /r /y
Put what you want in a batch script, set scheduler to run as often as desired. With this method you will always have a backup and all your computers will share the same profile data.