Solarious
Explorer
Whisperknife from Races of the Wild, as mentioned above, is a tailor-made PrC for throwers.
If you have the Complete Scoundrel and don't mind using a feat, picking up Daring Outlaw is good for: bumping up your BAB, getting Weapon Finesse for free, and improving Fortitude saves, as well as picking up Insightful Strike, all while maintaining sneak attack progression (which is typically 2d6 more, plus the incidental Grace and Dodge bonus). Also works well with Invisible Blade to make a single stat do some heavy lifting, and ensures your attacks won't completely suck after the 1st round is over. Also works with Palm Throw insidiously well.
Master Thrower is also worth staying in until level 5 for Weak Spot, to counteract the TWF Thrower attack bonus problems. Let's face it, most of the daggers are going to be non-magical, and you'll faceplant against the dreaded high AC target numbers (TWFs are infamous for missing a lot, especially on the irrative attacks, let alone TWFs that throw things). Besides, if you decide to use Palm Throw, you might as well get another really powerful ability that uses the exact same mechanical drawback, which is no drawback at all.
Theoretical build: Rogue4/Swashbuckler3/Master Thrower5/Inivisible Blade5/Ninja1 w/ Daring Outlaw. Not neccessarily in that order. Possibly replace Invisible Blade with more Swashbuckler, if you want to entertain the idea of using throwing weapons besides daggers (everyone loves their Naruto). Ninja is there because of Wis to AC at very high levels, working with no-armor Int bonus to AC. Very replaceable.
PS. Remember Weak Spot works only against creatures your size or larger, favoring Halflings... although you'll always want Reduce Person in combat anyways, which means it really doesn't matter that much. Many builds are possible, the best build for this one is... negotiable.
If you have the Complete Scoundrel and don't mind using a feat, picking up Daring Outlaw is good for: bumping up your BAB, getting Weapon Finesse for free, and improving Fortitude saves, as well as picking up Insightful Strike, all while maintaining sneak attack progression (which is typically 2d6 more, plus the incidental Grace and Dodge bonus). Also works well with Invisible Blade to make a single stat do some heavy lifting, and ensures your attacks won't completely suck after the 1st round is over. Also works with Palm Throw insidiously well.
Master Thrower is also worth staying in until level 5 for Weak Spot, to counteract the TWF Thrower attack bonus problems. Let's face it, most of the daggers are going to be non-magical, and you'll faceplant against the dreaded high AC target numbers (TWFs are infamous for missing a lot, especially on the irrative attacks, let alone TWFs that throw things). Besides, if you decide to use Palm Throw, you might as well get another really powerful ability that uses the exact same mechanical drawback, which is no drawback at all.
Theoretical build: Rogue4/Swashbuckler3/Master Thrower5/Inivisible Blade5/Ninja1 w/ Daring Outlaw. Not neccessarily in that order. Possibly replace Invisible Blade with more Swashbuckler, if you want to entertain the idea of using throwing weapons besides daggers (everyone loves their Naruto). Ninja is there because of Wis to AC at very high levels, working with no-armor Int bonus to AC. Very replaceable.
PS. Remember Weak Spot works only against creatures your size or larger, favoring Halflings... although you'll always want Reduce Person in combat anyways, which means it really doesn't matter that much. Many builds are possible, the best build for this one is... negotiable.