Do you have a microSD card in the slot?
I use this to test the SPI connection. If the serial monitor shows 192.168.2.2, then it is ok. If it shows anything else, like 0.0.0.0, then it failed.
#include <SPI.h>
#include <Ethernet.h>
byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
IPAddress ip(192,168,2,2);
void setup() {
Serial.begin(9600);
// disable SD card if one in the slot
pinMode(4,OUTPUT);
digitalWrite(4,HIGH);
Serial.println("Starting w5100");
Ethernet.begin(mac,ip);
Serial.println(Ethernet.localIP());
}
void loop() {
}