Brutal Barbarians is another great product in the Class Options series. Four appropriate and cool pieces of artwork, bookmarks (not something you always see in a 12-page PDF), and lots of good options for building alternate barbarians.
Black Rage is an alternate Rage similar, but different from, the old Frenzy option. The Wild Shaman feels something like a Barbarian-meets-Cleric or Druid, granting orisons, the domain powers of one nature-themed domain, and either Command Undead or Turn Undead instead of gaining the standard rage benefits. It's not an option for every character, but it definitely fills an interesting niche mechanically and flavor-wise.
Several new Rage Powers are introduced, including Brute Charge (count as one size category larger when bull rushing or overrunning), Enchanter's Foe (bonuses against a foe that tried to use an Enchantment spell against the Barb), and War Cry (grant self and allies an effect similar to the Bless spell with a shout). Great Hands may be a little too powerful, allowing a Barbarian to wield a weapon one sizes larger while raging, but this will depend how loose your group is. There are also a few options for a barbarian who wishes to have a mount here.
Which is good, because the very next thing we get is an alternate class feature called Horse Lord, adding to the movement speed of any mount the Barbarian rides instead of the Barbarian himself. Other options here include a weaker version of Favored Terrain or bonuses to Handle Animal, Knowledge (Nature) and Survival instead of Trap Sense, which always felt a bit weird on the Barbarian to me anyway. Mage hunting Barbarians may prefer Spell Resistance to Damage Reduction, and as in previous Class Options, we get alternate capstones. Painless, Spell Breaker and Battle Weaver are all very cool alternates to Mighty Rage.
The next idea is very interesting - Barbarian Bloodlines. Basically lists of specific rage powers based on the idea of a monstrous ancestry such as Basilisk, Cyclops, Genie or Troll, they also have Heritage Marks that are active even when not raging. I'm sorry to say I have to reduce my rating to 4 stars because some of the Heritage Marks seem too good, a +1 to natural armor or Cold Resist 5 for no apparent trade-off. I suppose the downside is that you HAVE to take a Rage Power associated with your Bloodline, which sometimes include subpar options like Low-light Vision or Raging Climber... actually you know what, forcing me to take Raging Climber in exchange for +2 AC at 11th level is totally fair. 5 stars it is.
Finally we get some feats, some relating to the bloodlines. Interesting ones include Iron Vitality (increase Str and Con even further while raging, but take Str and Con damage at the end of the rage), Naked Savage (intelligent foes take a penalty to hit you if you wear no or light armor), An Ancient Heritage (a bonus to knowledge skills for Barbarians?! I like it.) and a few more options for mounted Barbarians.
All in all, a great product, with lots of useful and flavorful options.
EDIT: Also a few nice options for unarmed Barbarians, if you're into that kind of thing.