Here are the default fuse settings for each Arduino from the boards.txt included with the Arduino development software.

To understand more about the fuse settings for your microcontroller, visit Engbedded’s AVR Fuse Calculator.

To write fuse settings, you will need a programmer with this capability. I use Mighty Ohm’s high-voltage rescue shield available here.

Arduino Uno

Low Fuse	0xFF
High Fuse	0xDE
Extended Fuse	0x05

Arduino Duemilanove or Nano w/ ATmega328

Low Fuse	0xFF
High Fuse	0xDA
Extended Fuse	0x05

Arduino Diecimila, Duemilanove, or Nano w/ ATmega168

Low Fuse	0xFF
High Fuse	0xDD
Extended Fuse	0x00

Arduino Mega 2560

Low Fuse	0xFF
High Fuse	0xD8
Extended Fuse	0xFD

Arduino Mega (ATmega1280)

Low Fuse	0xFF
High Fuse	0xDA
Extended Fuse	0xF5

Arduino Mini

Low Fuse	0xFF
High Fuse	0xDD
Extended Fuse	0x00

Arduino Fio

Low Fuse	0xFF
High Fuse	0xDA
Extended Fuse	0x05

Arduino BT w/ ATmega328

Low Fuse	0xFF
High Fuse	0xD8
Extended Fuse	0x05

Arduino BT w/ ATmega168

Low Fuse	0xFF
High Fuse	0xDD
Extended Fuse	0x00

LilyPad Arduino w/ ATmega328

Low Fuse	0xFF
High Fuse	0xDA
Extended Fuse	0x05

LilyPad Arduino w/ ATmega168

Low Fuse	0xE2
High Fuse	0xDD
Extended Fuse	0x00

Arduino Pro or Pro Mini (5V, 16 MHz) w/ ATmega328

Low Fuse	0xFF
High Fuse	0xDA
Extended Fuse	0x05

Arduino Pro or Pro Mini (5V, 16 MHz) w/ ATmega168

Low Fuse	0xFF
High Fuse	0xDD
Extended Fuse	0x00

Arduino Pro or Pro Mini (3.3V, 8 MHz) w/ ATmega328

Low Fuse	0xFF
High Fuse	0xDA
Extended Fuse	0x05

Arduino Pro or Pro Mini (3.3V, 8 MHz) w/ ATmega168

Low Fuse	0xC6
High Fuse	0xDD
Extended Fuse	0x00

Arduino NG or older w/ ATmega168

Low Fuse	0xFF
High Fuse	0xDD
Extended Fuse	0x00

Arduino NG or older w/ ATmega8

Low Fuse	0xDF
High Fuse	0xCA