Two-Weapon Defense

[dontpunkme]

Other good feats if you have the Feats book released by AEG (assuming your dm allows these feats)
Parry- if you have weapon finesse for the weapon you gain +1 dodge bonus to ac against all opponents you engage in melee with (no help on ranged weapons)
Parrying Weapon- when wielding light weapon that you have weapon finesse for you gain a +2 deflection bonus (if you have imp twf feat this increases to +4)
these feats can get extremely deadly when applied in conjunction with the following feats
Superior Finesse: use dex as bonus to damage instead of str
Superior TWF: You may use a med weapon in off-hand as if it were a light weapon

I'm not even going to begin describing the damage this allowed my TWF Fighter do in conjunction w/ Weapon Mastery and Elite Weapon Mastery and a pair of scimitars.

If you haven't purchased Feats yet, then I'd highly recommend it especially if you like TWF as I feel the WOTC products left a lot to be desired.

 

[xazil]

Animated shields still count as if the character were using them, including ASF and any penalties for using a shield (for instance, the loss of all monk abilities). The TWD tree doesn't suffer these limitations.
Also, animated shields cost gold. TWD is free.

While I'm not a big proponent of animated shields in most cases they are better. Characters who can afford to use up the feats for both the two weapon fighting feats and the defense feats is are going to usually be fighters or maybe a two weapon ranger. If you are a caster and are using two weapons you can't cast a S or M spell as you need a hand free, regardless of ASF. As noted above, improved buckler defense with a mithril buckler is probably the way to go for casters.

In terms of gold TWD is free, but if you look at what resources characters get and how many, then the TWD tree is much, much more expensive. Feats are a very limited resource for most compared to the gold amounts at mid to high levels.