Good ways to dual wield in 3.5

[No brains]

I heard once before that TWF is severely gimped in 3.5. Are there any good ways to do it? I feel like there are benefits to having more attacks, but I also know that the gold and build costs can be pretty steep.

[BowStreetRunner]

It's not so much that TWF is gimped (it is still strictly superior to sword and board or one-handed fighting) but rather that two-handed weapon use benefits from some serious damage multipliers. So if you want TWF to be a viable alternative, you have to be able to get your damage-per-round up to equivalent levels, which is not always an easy thing. THF has access to many of the same options that TWF does, plus many that aren't usually available to TWF (like power attack).

[Soranar]

The most efficient TWF I've seen is basically two handed fighting +

A friend of mine was playing a ranger so he got the TWF tree for ''free''
He still used a two handed weapon as his main weapon but
he used armor spikes as his secondary weapon, letting him optimize his combat the typical way (ubercharging)

The armor spikes did make a difference, often enough a creature was almost dead after the Two handed weapon hit and the little extra damage provided by the armor spikes did the trick

But sometimes it was also completely overkill...

Other than that a throwing build benefits greatly from TWF but keeping enough ammo on hand is pretty difficult only a DM is nice enough to let you enchant something that creates thrown weapons to make magical ammo as often as required (say gloves of endless javelins but with a more useful weapon like shurikens or knives)

[Darrin]

Obligatory link:

TWF OffHandbook (http://www.giantitp.com/forums/showthread.php?279079-3-5-The-TWF-OffHandbook).

To reiterate what BowStreetRunner and Soranar have already said, the most effective way to TWF is to wield your primary weapon two-handed, and use something like armor spikes or unarmed strike as your offhand weapon. I prefer unarmed strike, as you can still apply Power Attack damage with it, but it costs a feat and can be hard to fit into a feat-heavy TWF build. This strategy is basically your standard UberCharger build (Power Attack, Improved Bull Rush, Shock Trooper, Leap Attack, etc.) plus something extra.

There are some other methods that can match pace with the UberChargers. For example, the Exotic Weapon Master has a stunt called "Uncanny Blow". It's not entirely clear what the designers intended, but it could be interpretted to mean that when you wield an exotic one-handed weapon in one hand, it's treated as two-handed for the purposes of Power Attack. It works best with Oversized Two-Weapon Fighting (one-handed exotic weapons in each hand), but is also pretty feat-intensive.

The third method of getting two-handed damage multipliers on both weapons is the Revenant Blade PrC. This one's pretty solid, although you have to be a Valenar elf and wield a double scimitar.

The other popular methods to make TWF somewhat worthwhile, ranked haphazardly by effectiveness:

Bardblade with Dragonfire Inspiration. More effective than precision-based bonus damage because you don't have to worry about any special conditions to trigger it, and there's no range restriction.

Swift Hunter builds. I like these a lot, but it requires a lot of levels and feats to be taken in a very specific order.

Sneak Attack builds, such as Daring Outlaw. Lots of damage if you can trigger it reliably, but gets boned pretty hard with a lot of creature type immunities and various counters.

[Anthrowhale]

Bloodstorm Blade 4 may solve the wealth problem of TWF by catching a Lightning Ricochet in the off hand. It's a little sketchy because you need two weapons to do two weapon fighting. To deal with that you could Quickdraw(free action) some cheap/light weapon in the offhand to qualify then drop it(free action) before catching the Lightning Ricochet in the off hand.