Here are my thoughts about barbarian races...
Human: Humans make good barbarians, but then again, humans can excel at any class. The free feat you recieve for being a human will come in useful, since barbarians don't recieve any bonus feats.
Dwarf: Dwarves make excellent barbarians. Their +2 Con gives them a boost to their hit points and fort saves, and also allows them to remain in range longer. Their slow movement speed is offset by the barbarian's fast movement, and a dwarf barbarian can wear medium armor and carry heavy loads without being slowed down. Dwarves also recieve saving throws against spells and poisons, dodge bonuses against giants, stability bonuses against being tripped or overrun, and attack bonuses against orcs and gobinoids. A dwarf barbarian will be very difficult to kill.
Half-Orc: It's possible for a half-orc barbarian to have 20 Strength at level 1. A half-orc barbarian using a greatsword or greataxe along with the Power Attack feat is capable of dealing tremendous amounts of damage.
Elf: Elf barbarians aren't particularly great. Their penalty to Con reduces their hit points (and barbarians need lots of hit points, as they'll be getting hit a lot), and also reduces the length of their barbarian rages. The dex bonus, resistance to enchantment spells, and immunity to sleep are useful, but not useful enough to make elves good choices for barbarians.
Half-Elf: Half-elves aren't particularly great as barbarians, but then again, half-elves aren't particularly good at anything.
Halfling: Halflings make decent barbarians, although their small size and penalty to strength means that they won't be inflicting as much damage as a medium-sized barbarian. The extra dexterity and AC bonus due to size can be useful to barbarians, as can the bonuses to saving throws.
Gnomes: Much like halflings, gnomes are hindered by their small size and low strength. Gnomes do recieve a bonus to Con, which helps their hit points and ability to rage, as well as attack bonuses against kobolds and goblinoids, and dodge bonuses against giants. Gnomes make average barbarians.