Farnell
(in Italy) http://it.farnell.com/jsp/home/homepage.jsp
(In UK) http://uk.farnell.com/jsp/home/homepage.jsp
RS Components
(In Italy) http://www.rs-components.it
(In UK) http://rswww.com
Robot Italy
(In Italy) http://www.robot-italy.com
Smart Projects
(In Italy) http://www.smartprojects.it
Arduino
(Sources world-wide) http://arduino.cc/en/Main/Buy
Sparkfun (USA site with all kinds of interesting stuff. You can also buy stuff but takes a time because of Italian customs)