What books are allowed? You would do well with the c.Champion Lion Totem Barbarian variant, so you can do a pounce on a charge and full attack, in trade for fast movement. Oversized Two-Weapon fighting might be a better feat than Monkey Grip for you, and in fact I'm pretty sure Monkey Grip explicitly does not help the off-hand. Even if it does, it's a really weak feat.
The Strongarm bracers cost 6000 gp from Magic Item Compendium and let you use a weapon one size larger than normal, that could also help you.
For prestige class? Not sure. There's a cool Elf-only barbarian class in Races of the Wild for 2-weapon users called the Wildrunner. Otherwise...Frenzied Berserker doesn't suck.