Weapon EnchantmentsBerseker (UE): +2 weapon's enchantment while raging.
Furious (OA): rage bonuses increase a step.
Fury (?): +1d6 damage while raging.
FeatsBlazing Berserker (SS): gain the fire subtype while raging.
Extend Rage (CW): +5 rounds.
Extra Rage (CW): +2 per day.
Instantaneous Rage (CW): free action to rage.
Intimidating Rage (CW): free action demoralize once per encounter.
Destructive Rage (CW): +8 to break stuff while raging.
Frozen Berserker (FB): gain the cold subtype while raging.
Mad Foam Rager (PHBII): delay a single attack that hit you by one round.
Reckless Rage (RoS): -2 AC, +2 str/con while raging.
Stone Rage (RoS): +1 enhancement bonus to AC while raging
ItemsBands of Blood Rage (MiC 202): 3/day you/allies "blood rage" for +5 moral to damage, not a real barb item but the flavor is the same.
Mantle of Rage (
Online): +1 rage per day, or gives rage if you lack it.
Specific WeaponsAxe of Anger(A&E): +2 to rage duration.
Berserker Blade (FR:MoF): +1 to the enhancement while raging and it's a +2 bastard sword for only 11k.
Soldier's Rest (A&E): Ignore fatigue while holding it, spiffy.
Trident of Serenity (FR:RoF): Blocks rage, and frenzy. Give it to a party member you don't want to kill.