I think it's good to have a BiS thread I can bookmark and look up if I need to check items quickly when finding them or planning a purchase.
I plan to concentrate on items who give the best unbuffed dps or overall best stat-budget. Of course this can change for different builds, but I'm planning to update this thread on a regular basis (and possibly for different builds). I'm not the best wizard in town, so feel free to add your own 2 cents.

The following items are considered BiS. Rare items can of course be used, but right now you're more likely to find a legendary than a rare with comparable stats. Just take the max rolls on these as a reference point.
As a general rule, you want items that have INT + CRIT CHANCE + CRIT DAMAGE + ATTACK SPEED on it.

* Updated Sept. 21th 2012 *

(First in list = highest potential for overall best rolls)

Helm:
  1. Tal Rasha's Guise of Wisdom
  2. Mempo of Twilight Can get better rolls than Andy's if you're lucky
  3. Andariel's Visage Guaranteed CRIT and IAS


Amulet:
  1. Tal Rasha's Allegiance


Shoulders:
  1. Vile Ward Aside from high INT and ALL RES, not so special but at least they look cool.


Chest:
  1. Tal Rasha's Relentless Pursuit Absolute BiS. No way around it.


Gloves:
Right now rares seem to be the absolute BiS for this slot. Look for 150+ INT, 8%+ CritChange, 50% CritDamage and 8-9% IAS

Wrist:
  1. Lacuni Prowlers Guaranteed IAS and Movements speed. Look for additional INT and CritChance


Rings:
  1. Zunimassa's Pox Zuni Ring and Boots are the preferred items to get our +130 Int bonus from this set.
  2. The second slot can be any rare ring with our standard stats. AFAIK other leg/set rings dont roll all 4 of our desired stats right now.
  3. ​Stone of Jordan Depending on the rolls, the dps gain won't reflect on your stats immediately. Still, the guaranteed 20-30% increased damage against Elites makes this ring a real killer.


Belt:
  1. The Witching Hour Absolute BiS. Guaranteed INT, IAS and CRIT DAMAGE. You just need to get lucky with the other rolls


Pants:
  1. Inna's Temperance A Monk/DH set? Of course, if you value dps over survivability! These pants always have the dex affix on them, so you'll want these to roll with Int and make sure IAS is at 9%. 1% Crit is not much, but it's nice to have, too!
  2. Depth Diggers Those pants back you up with with high all res and if you're lucky high INT and VIT. Guaranteed MF & GF. Rare pants are fine, too.


Feet:
  1. Zunimassa's Trail Needed for our setbonus (if you're going for it).
  2. Otherwise you can use Ice Climbers if you get lucky rolls.

Weapon:A good rare wand with 1200dps, 80-100% crit damage and socket will be the best right now, but they are harder to find than a needle in a hayball.
  1. Chantodo's Will Standard choice for most builds
  2. Echoing Fury If you don't need AP on crit (like when playing Archon builds) you should totally go for this weapon. Beastly.
  3. ​Slorak's Madness IMO a very good wand but looking at the AH it's very rare to get a good roll on the DPS. Many 800dps versions with otherwise perfect stats are often available on the AH for as low as 25mill (EU)!


Source:
  1. Chantodo's Force
  2. Tal Rasha's Unwavering Glare Probably the coolest looking source in the game.
  3. Triumvirate Very nice source for Archon builds because of the increased Arcane damage.