Update 11:00 CEST - Added today's blue posts.
Update 03:30 CEST - Added a picture for the Chef's Hat and a change to the Death Knight Tier 7 Set Bonus
There will be a small change to the website, probably tomorrow. If you experience any (new) bug please report it to the Suggestions and Feedback forums. (No, we are not updating the site with a Hello Kitty theme on April 1st, this is a real update!)
Patch 3.1 - PTR Build 9742
A new build has been deployed on test realms, it looks like a minor build so I wouldn't expect too many changes from it.
Talent Calculator
The Talent Calculator has been updated to the latest build.
Achievement Changes
Raids & Dungeons

• Glory of the Raider no longer rewards the Plagued Proto-Drake.
• Heroic: Glory of the Raider no longer rewards the Black Proto-Drake.

Raids & Dungeons - Ulduar

• Never Stand Near the Faceless Dude has been removed from the game.
• Heroic: Never Stand Near the Faceless Dude has been removed from the game.
• Observed now rewards a new Title: Starcaller
• Herald of the Titans *New* - Defeat Algalon the Observer on Normal Difficulty without anyone in the raid wearing any equipment with an item level higher than 226. Title Reward: Herald of the Titans
• Heroic: Observed now rewards a new Title: The Astral Walker

Cooking

• Cooking with Style - Obtain a Chef's Hat. (Screenshot)

Feats of Strength

• Deadly Gladiator - Achieved Deadly Gladiator title.

Spell Changes

Quote from Blizzard staff

Death Knight (3.1 Skills List / 3.1 Talent + Glyph Calc.)
Blood

• Blood Boil range has been reduced from 20 yards to 10 yards.
• Will of the Necropolis now cannot be triggered by damage which deals less than 5% of your health.

Frost

• Rime now procs from Obliterate instead of Icy Touch.

Unholy

• Death Strike damage has been increased and now deals 75% weapon damage (up from 60%) plus 222.75 (up from 178.4) for the max Rank.
• Anti-Magic Shell now absorbs the damage dealt by harmful spells up to a maximum of 100% of the Death Knight's Health. (Up from 50%)
• Summon Gargoyle now lasts up to 40 sec. (Down from 1 min)
• Ghoul Frenzy now Grants your pet 25% haste for 30 sec (up from 15 sec) and heals it for 60% (up from 30%) of its health over the duration.

Glyphs

• Glyph of Heart Strike - Your Heart Strike also reduces the movement speed of your target by 50% for 10 sec. (Up from 5 sec.)

Tier 7 Set

• DPS Set - 2 pieces - Increases the critical strike chance of your Obliterate, Scourge Strike and Death Strike abilities by 5%. (Old - Didn't affect Death Strike)
• DPS Set - 4 pieces - Your Obliterate, Scourge Strike and Death Strike generate an additional 10 Runic Power when used.

Druid (3.1 Skills List / 3.1 Talent + Glyph Calc.)
Balance

• Moonkin Form now costs 13% of base mana. (Down from 22%)

Feral

• Rend and Tear now increases the critical strike chance of your Ferocious Bite ability on bleeding targets by 5/10/15/20/25%. (Down from 10/20/30/40/50%)
• Primal Tenacity now reduces fear effects duration and damage taken while stunned while in Cat Form only.

Priest (3.1 Skills List / 3.1 Talent + Glyph Calc.)
Shadow

• Psychic Horror now makes the target drop its main hand and ranged weapons for 10 sec. (Old - All Weapons)

Warlock (3.1 Skills List / 3.1 Talent + Glyph Calc.)

• Everlasting Affliction tooltip has been corrected to remove Siphon Life.

10-Man Ulduar Achievements

Quote from: Bornakk (Source)

Having a hardcore 25player guild getting both the 25 and 10 player realm firsts doesn't seem right. We want there to be an end goal for each one to shoot for, if you want to run both, that's up to you - but this way the guilds that only run the normal version have an end goal to shoot for that the hardcore 25 player guilds can't swipe.
To try and clear up any confusion, the planned item level for the achievement in Ulduar 10 is item level 226. This level gear drops from both hard mode Ulduar 10 and regular boss kills in Ulduar 25. So yes, while players who clear Ulduar 25 will get more 226 gear at a faster pace and possibly get this achievement first, it's an achievement anybody can do, so when a guild that only runs normal Ulduar 10 progresses through the instance and gets the hard modes done, they will be ready to take on this achievement.
Reward: Herald of the Titans (title)
If you primarily run 25 player instances and want to get this achievement/title, just hang on to your Kel'thuzad weapons and regular Ulduar 25 boss kills and you should be good to go.
[...]
The discussion (at least as far as I know, it's been all over the place) is about how we removed the Ulduar 10 player "realm first" feats of strength and we are working on replacing it with something else.
We are looking to replace these 10 player "realm first" feats with a regular achievement that anybody can do but is focused on being the pinnacle of progression for players who focus on 10 player raids while minimizing the advantage that players have in heroic 25 player raids.

Blue posts

Quote from Blizzard staff

Additional Frostwyrms in 3.1
No additional frost wyrms are being added in patch 3.1, we will see what the future holds beyond that. (Source)
Noblegarden in 3.1
There are a few things to note:

• The new version of Noblegarden lasts one week, not one day.
• If you're looking at previous maps put together for egg-hunting, they're not going to be very effective. Eggs are spawned solely around the level 5ish towns (Goldshire, Brill, etc.) and there are always eggs up, even if many people are farming them. If you haven't found them, it isn't a matter of spawning... it's a matter of you not finding them. (Source)

Arena Season 6: One-week grace period at the end of Season 5
There will be a week between the end of season 5 and the start of season 6 where players will have time to spend points they've earned. In other words, you'll have one week from the day 3.1 hits to spend your points.
This confuses me a little - let's say hypothetically season 5 ends tomorrow - from your wording, season 6 will start the next tuesday. So there'll basically be a "dead" week for arena when there is no season going on at all?
Correct. We're giving a one-week grace period for players to spend accumulated points from season 5 since we're wiping them at the start of season 6. (Source)
Dual Specialization and Buffs
If you have a buff on you that another player cast, it should not go away when you switch specs.
If you have a buff tied to a particular talent spec, it will go away on you when you switch specs.
If you have a buff tied to a particular talent spec, it will generally not go away on the rest of the group. The general rule here is it’s as if you left the raid. So paladin blessings (which go away if you leave the raid) will go away. Improved Fortitude will not go away if you change specs to a spec without Improved Fort (though it will fall off of you), as those stay when you leave the raid. (Source)
No walking animation on Hippogryphs
It can land, however, the Hippogryph just doesn't like to get its feet dirty. Joking aside, this is something that we've been aware of, and it's just low (very) on the list of things to address. (Source)
Amani War Bear bugfix in 3.1
I looked into it and this is something we are aware of and working on changes. The problem is that we are working on setting this up so it works properly for all races. Going from a gnome to a tauren is quite a bit of different in size which affects the character and their positioning. We will see where it ends up when 3.1 launches. (Source)