http://forums.worldofwarcraft.com/thread.html?topicId=19820412001&sid=1&pageNo=1#3:

• The Faction Champions encounter in the normal 10-player and normal 25-player Trial of the Crusader instances have had a number of spells and abilities altered which should result in less overall damage. (Kyth: note this doesn’t include heroic)
• The Anub’arak encounter has been changed on all difficulties. Anub’arak now attacks faster, the Nerubian Burrowers should hit a little harder, and their Expose Weakness ability now caps at 9 stacks. (Kyth: all difficulties. Supposed Expose Weakness is also only +25% now instead of +30%, but I don’t have actual in-game confirmation.)
• Some season 7 arena weapons will now have a socket.
• Threat of Thassarian will now properly halve the damage of Rune Strike for the off-hand strike.
• Soulstone Resurrection now fades upon entering raid combat if the character who cast it is not present.
• The Idle/Inactive debuff is now cleared upon round switches in Strand of the Ancients.
• The Mistress of Pain will now target more accurately in the 25 man Heroic Jaraxxus encounter.
• The damage of Hunter’s Volley ability has been increased.

Just one this time:

7/1/09

• In the Mimiron encounter, the abilities Rapid Burst and Hand Pulse no longer cause spell pushback.

Some substantial nerfs today:

6/11/09

• The Yogg-Saron encounter has received the following changes: Death Ray no longer hits players who are under the effect of Malady of the Mind, Guardians of Yogg-Saron no longer use Dominate Mind, the spawn rate of Guardians of Yogg-Saron is more forgiving, and these Guardians will no longer spawn if a player that is protected by Hodir’s Flash Freeze hits an Ominous Cloud.
• In the opening sequence of Ulduar you can now see Liquid Pyrite from farther away.
• The Flame Leviathan encounter has received the following changes: the bonus health Flame Leviathan receives per tower has been reduced, the ejection height from Flame Leviathan has been reduced, the snare effect of the Tower of Frost has been removed, and the cannons on Demolishers and Siege Enginers should now break Flash Frozen vehicles in 1 shot.
• The XT-002 Deconstructor encounter has received the following changes: the health of the heart has been slightly reduced in heroic difficulty and the rate at which Gravity Lapse and Searing Light are cast has been reduced.

6/01/09

• The tentacle creatures and floating skulls in Yogg Saron’s brain rooms should now load faster.
• The following items have had their stats increased to properly reflect their item level: Earthshaper, Valorous Siegebreaker Shoulderplates, and Conqueror’s Siegebreaker Shoulderplates.
• The Leviathan’s Coil ring has had its armor reduced from 882 to 448 to properly reflect the item level.

4/29/09

* Fixed an issue where Mimiron could randomly change targets while casting P3Wx2 Laser Barrage in phase 4. It is still possible for it to appear that he is turning quickly for an instant to shoot another direction, but this is just a visual bug that will be resolved in a future patch.
* The Auriaya encounter has received the following changes: the damage of Strength of the Pack has been increased, the duration of Terrifying Screech has been reduced, the damage of Sonic Screech has been reduced, and the damage from Seeping Feral Essence has been reduced.

4/28/09

* Pure Saronite mining nodes have temporarily been disable in Ulduar and will return in the future.
* The effectiveness of the Priest spell Divine Hymn has been reduced.
* The Priest ability Soul Warding now only reduces the mana cost of Power Word: Shield by 15% instead of 30%. The tooltip for this spell will be updated at a later date.
* Glyph of Mass dispel will now reduce the cost of the spell by only 35%.
* The Emalon encounter has received the following changes: The total health of the Tempest Minions has been reduced and Emalon’s Chain Lightning spell will now have a limit on the number of targets it can hit.
* The Ignis the Furnace Master encounter has received the following changes: The interrupt effect and duration of the damage from Flame Jets has been reduced, the damage from the Slag pot has been reduced, the number of Heat stacks needed to transform an Iron Construct into a Molten state has been reduced, the base melee damage done by Ignis has been reduced, and the damage bonus Ignis receives from Strength of the Creator has been slightly increased.
* The Assault Bots on the Mimiron encounter will now attack faster, in turn they will do less damage per hit.
* Spring Flowers will not cast or go on cooldown if the target already has the buff.
* The XT-002 Deconstructor encounter has received the following changes: The duration of Tympanic Trantrum has been reduced, the timer for XT-002 to hit berserk has been increased, the damage of Light Bomb has been reduced, the effect radius of Light Bomb has been reduced, and the health of XM-024 Pummeler has been reduced.