all machines:
  /etc/modules.conf:
    alias char-major-89 i2c-dev

Some representative machines:

glow-c006:
  /etc/sysconfig/lm_sensors:
    MODULE_0=i2c-i801
    MODULE_1=i2c-isa
    MODULE_2=max6650
    MODULE_3=eeprom
    MODULE_4=w83627hf

glow-c067:
  /etc/sysconfig/lm_sensors:
    MODULE_0=i2c-piix4
    MODULE_1=w83781d
    MODULE_2=smbus-arp
    

in addition to the above config updates the system also needs to link 
/etc/init.d/lm_sensors to the default runlevel, and if the system
isn't rebooted this script will need to be run before 'sensors' will
work