Thanks silasmoeckel for clearing my concepts.
I will use the ethernet anyway and I will follow researching about eeprom and the SD advantage related to my project.
For the EEPROM i found this: Recommendations For You - DealeXtreme
For the USB host I found this: http://www.circuitsathome.com/arduino_usb_host_shield_projects
so:
read from the device -> save into EEPROM -> connect the USB pendrive and save the data into a file.
It's possible or I am insane?.
Thanks for all help.
Akuthor