protection against sneak attack

[rye0006]

what items, or spells are there to protect a party against sneak attacks were you to be foolish enough to attempt to infiltrate/destroy a rogues guild?

[LordBlades]

anything that grants concealment (like minor cloak of displacement).
Also, heavy fortification (easy to get by casting all Heart of X spells on yourself)

[JaronK]

Being a Necropolitan (undead) will do it. Just disguise yourself as something living and they won't know why it doesn't work (and won't think to try Grave Strike).

JaronK

[dsmiles]

Don't get caught flat-footed? Always fight from a corner? Ring of Greater Invisibility?

[mint]

Even better, disguise yourself into something undead! If they don't know you have vital organs they won't be aiming for them.
Which poses an interesting question:
Do you have to declare sneak attack to sneak attack by RAW?

[Curmudgeon]

Do you have to declare sneak attack to sneak attack by RAW?
No. D&D doesn't (except in a few rare cases) use declared actions.

A Rogue with the Penetrating Strike alternative class feature is still going to do ½ the normal sneak attack dice in damage when they flank a target that's normally immune to sneak attack, whether the Rogue is aware of that immunity or not.

[Cyrion]

Look for opportunities to pick up Uncanny Dodge. Rogues get it (perhaps not helpful if you're going after a rogues' nest), but so do warblades and probably a couple of other classes.

In addition to things that give you fortification or turn you into undead, becoming a construct is also a possiblity.

Really your best bet is not to get caught flat-footed or get flanked. To avoid the first, judicious use of divination and abjuration spells will helpful, and planning your combat tactics so that nobody can be flanked solves the second.

[Spiryt]

Two levels in Barbarian are pretty easy option from less complicated ones.

[Person_Man]

The Fellmist Robe soulmeld grants 10 + 5*essentia invested (max 50%) concealment against attacks made by non-adjacent enemies (ie, 5 feet or more away from you). If you bind it to your Soul Chakra, it works against everyone. But that's not really necessary. Even at 1st level, a non-incarnum using character can take the Shape Soulmeld feat and get all day 10% concealment, and use any battlefield control combo to keep people away from getting next to you. (This works particularly well if you're a caster or similar ranged build). Thus you're functionally immune to precision damage (unless they have the Pierce Magical Concealment feat) and have a minor but still helpful defense for the cost of just 1 feat.

On a similar note, the Winged Warrior feat (Races of the Wild) allows you to create a hemisphere of concealment (for those in the cloud) and total concealment (for those trying to attack into or through the cloud) around you for 1 round as a Move Action. Again, works great for spellcasters. Only down side is that it requires wings, the Hover feat, and +4 BAB. So you either need to be a Dragonborn or Raptorian, or invest in a feat or a graft to get them.

[Curmudgeon]

The Fellmist Robe soulmeld grants 10 + 5*essentia invested (max 50%) concealment against attacks made by non-adjacent enemies (ie, 5 feet or more away from you). If you bind it to your Soul Chakra, it works against everyone. But that's not really necessary. Even at 1st level, a non-incarnum using character can take the Shape Soulmeld feat and get all day 10% concealment, and use any battlefield control combo to keep people away from getting next to you.
Note that this item creates what it terms "minor concealment" (10% miss chance). According to the Player's Handbook rules concealment (without the "minor" modifier) (20% miss chance or more) prevents sneak attack, so this one is subject to DM interpretation.

[Choco]

Anything that makes you immune to critical hits. Heavy Fortification has been mentioned, 1 level in Warshaper will do it, become undead, etc.