This is a guide for purely feral druid dps. A separate guide for Feral tanking will be generated.

1. Talent Build
http://www.wowhead.com/?talent#0ZEMMcfrz0eR0huikbyczb:VmpV0z
The ICC feral build I use currently. Gives the max amount of dps available.
Improved Mangle 3/3 is useless if you have a trauma/mangle bot.
Feral Aggression starts to look like an attractive talent when Ferocious Bite is able to reach 20k crits.
Improved Mark of the Wild is a free talent sorta. The extra 1% to all attributes is pretty decent, but not necessary. If you feel 1% increase to attributes is not that great, then you could put it in Feral Aggression for another 3% damage to Ferocious Bite.
Primal Gore is a very delicious talent. After 3.1, this has insanely buffed up kitty sustained dps. Crits can deal from 4k-5k in pve and about 1.5k-3k in pvp every 2 seconds.

http://www.wowhead.com/?talent#0ZgGMcfrz0eR0huikbyczb:VmpV0z
This is the build for Naxx and Pre-naxx where aoe would be better.
Basically just moved 3 points from Feral Aggression to Feral Instinct. This gives 30% extra dmg to kitty swipe which is pretty nice for aoe currently.

2. Glyphs

Major
These 3 glyphs are the must-haves of Feral dps.

Glyph of Rip - Awesome glyph since Primal Gore came out in 3.1 and helps ease up on the rotation a bit.

Glyph of Shred - Increasing the length of Rip again is awesome. Combined with Rip, you're sustained dps will shoot up.

Glyph of Savage Roar - You want Savage Roar to have the maximal uptime it can get. It makes your rotation easier as well.

Minor(Copy and pasted from bear guide)

Glyph of Unburdened Rebirth - ONE EXTRA FREE BAG SLOT.(Woot!) That's all I gotta say.

Glyph of Dash - More of a pvp glyph but I love it when you need to kite something while running your ass off.

Glyph of Aquatic Form - Self explanatory

Glyph of the Wild - Useless! You always have time to drink before a raid boss pull and improved leader of the pack gives you back mana for your crits.


3. Gear List

Naxxramas 25, Malygos, and Sartharion

Both Bear and Cat Gear
Belt of the Tortured
Tunic of Indulgence
Cover of Silence
Chestpiece of Suspicion
Sinner's Bindings
The Jawbone
Spaulders of Egotism
Leggings of Fleeting Moments
The Undeath Carrier
Chestguard of the Recluse
Mark of Norgannon
Concealment Shoulderpads
Leggings of the Honored

Bear Gear
Cloak of the Shadowed Sun
Defender's Code
Origin of Nightmares
Heritage
Dislocating Handguards
Hood of the Exodus
Thrusting Bands
Footwraps of Vile Deceit
Gatekeeper
Boundless Ambition


Cat Gear
Fool's Trial
Ruthlessness
Strong-Handed Ring
Aged Winter Cloak
Grim Toll
Stalk-skin Belt
Dawnwalkers
Cryptfiend's Bite
Idol of Worship
Infectious Skitterer Leggings
Gloves of Fast Reactions
Drape of the Deadly Foe
Journey's End
Frosted Adroit Handguards
Fury of the Five Flights

Tier gear is not listed, but it usually has really nice stats for tanking which is better than some of the non-tier pieces.

Items listed under Bear and Cat can still be used for Cat dps. This list does not tell you which is better than others, but the general rule comparison for upgrading is look to see if Agility>Strength>Attack Power>Crit Rating>Armor Penetration. If it's a tough choice for upgrading, you can use the program Rawr.
http://www.codeplex.com/Rawr

This program helps you see what gear is available to upgrade to and from where. Take it with a grain of salt though, sometimes it emphasizes too much of some stats such as armor penetration being insanely overpowered. I'll talk about armor penetration in the stats section.

Best in Slot Kitty Gear(Pre-Ulduar)
Valorous Dreamwalker Headguard
Favor of the Dragon Queen
Valorous Dreamwalker Shoulderpads
Drape of the Deadly Foe
Valorous Dreamwalker Raiments
Sinner's Bindings
Valorous Dreamwalker Handgrips
Jorach's Crocolisk Skin Belt
Valorous Dreamwalker Legguards
Dawnwalkers
Surge Needle Ring
Strong-Handed Ring
Darkmoon Card: Greatness
Grim Toll
Journey's End
Idol of Worship

4. Stats and Gemming

Stat

When you're upgrading you're gear, the general rule for comparison is to look at Agility>Attack Power>Crit Rating>Armor Penetration>Strength.

Agility - Still experimenting how much agility is needed but still one of the best stats for a cat. Gives Attack power and crit in cat. After some reading though, 70% crit is like the soft cap for crit, but really difficult to reach.
Strength - If you think you have enough agility, strength is the way to go. You get 2 ap for each point of strength and ap is multiplied when in cat form.
Attack Power - Same as Strength but you benefit more attackpower from Strength.
Crit Rating - Alot of your damage is based on yellow damage crit. As I said earlier, soft cap for crit is about 70% and you can never go wrong with more crit/agility.
Armor Penetration - Blizzard recently announced that they'd like to make Armor Penetration a really nice stat for feral druid kitties. There's some argument that armor penetration can be easily capped. The cap is just 100% armor reduced. Sunder and faerie fire is not included in this calculation. So do not include it in your quest to get 100% armor reduced. Some feral druids are able to pull out some nice numbers with just 80-90% armor penetration w/ grim toll proc.
Hit Rating - The current hit cap for feral druid kitties is 8%. BBBB states that it's 9% needed but after my own calculations, 8% is all you need. I have never missed a target when I have 8% hit rating(except for dust clouds on archavon that's supposed to drop your hit). 8% hit translate to 263 hit rating. I strongly encourage getting hit capped.

Expertise Rating - The soft cap for expertise is 6.5% for eliminating dodge. As a feral kitty with the Primal Precision, you only need 4% expertise, which translate to 132 expertise rating. The parry cap for expertise is 16% but there really isn't a point to getting parry cap when you spend most of your time behind the boss. Yes, the best position to dps is directly behind the boss. There are fights in Ulduar where you are fighting from the front and make expertise an attractive stat, but that can be excluded for now. With 132 expertise rating, it is guaranteed that you're attacks won't be dodged(unless there is a boss fight that lowers your expertise).

Gemming

Meta: Relentless Earthsiege Diamond
Red: Delicate Scarlet Ruby > Fractured Scarlet Ruby > Bold Scarlet Ruby
Yellow: Deadly Monarch Topaz
Blue: Shifting Twilight Opal

Edited:
I've changed my gemming rules quite a bit. For one, I have pushed out Strength as a possible gem. I don't push AP that much nowadays. I would start by gemming for hit/expertise. Once that is out of the way, Agility until you hit about 50-55% crit and then switch red gems to Armor penetration. I would limit myself to around 80-90% armor penetration and start gemming some more agility again. You can go for the 100% armor reduction but I feel that 80-90% is sufficient and you might start losing dps by losing some agi.



5. DPS Rotation

With the current cat rotation, this is what you're dmg should consist of:

As you can see the rotation is rather complicated.

Rotation:
A )Start - Faerie Fire(If no one else)>Mangle(If no other feral druids or arms warrior is around)>Rake>Savage Roar
B )If you have less than 30 energy - Tiger's Fury or Berserk
C )Shred until you reach 5 CP while keeping up mangle and rake. Save Clearcasting procs for Shred.
D )When you have 5 CP again,
- Savage Roar, is less than 7 seconds left
- Rip, is less than 5 seconds left
- Ferocious Bite, Savage Roar has more than 7 seconds and Rip has more than 5 seconds.
E )Return to B and C
Yes this sounds complicated and it is. It requires having a good eye. Even I have trouble sometimes and I mess up on the rotation. But keep watching those buffs, CP and debuffs and stay behind the target. The reason why Savage Roar is 7 seconds vs Rip being 5 seconds is that you want Savage roar uptime to be close to 100%. Losing 2 seconds where Rip is not up isn't too much of a dps drop since Ferocious Bite can crit pretty high(ranging from 10k-20k in naxx 25 gear).



Video for Cat Rotation
http://www.4shared.com/file/104032995/74015652/rotation2.html
Needs to be downloaded to show the whole thing. Preview only shows parts of it.

6. Addons:
CooldownCount - Puts the big numbers on cooldowns on the abilities as well as the numbers on the debuffs on target.
SmartyCatManaBar - Not used in pve content too much, but it's convenient to know what your mana is when you're in bear or cat form so you know if you can Battle Res or pop Tranquility.
Omen Threat Meter - Let's you see your threat and let's you know if you need to back off or use Cower(which I haven't had to use since BC)
Outfitter - Great for setting up gear and changing it automatically to dps or bear if you need to.
RatingBuster - Breaks down stats on an item to make it easier to compare to what you are wearing. For Cat and Bear gear, make sure to be in cat or bear form before you compare. Otherwise it is just making the comparison in your caster form, which is sometimes inaccurate.
Buttontimers - I recently picked this up as a timer for watching buffs and debuffs such as Savage roar, Rip, mangle, rake.


7. Resource:
Wotlk Diminishing Returns
Rawr
Big Bear Butt Blogger
Druid Wiki
Elitist Jerks

Could I get this stickied as well please?

Updated with cat rotation video.

3.2 Changes
* Mangle: Ranks 4 and 5 base points reduced by about 11%. Scaling from attack power unchanged.
* Rake: Ranks 6 and 7 base points on initial and periodic damage reduced by about 7%. Scaling from attack power unchanged.
* Rip: Ranks 8 and 9 base points and points per combo point reduced by about 6%. Scaling from attack power unchanged.
* Savage Defense: The animation for gaining this buff will no longer make the bear stand upright
* Shred: Ranks 8 and 9 base points reduced by about 10%. Scaling from attack power unchanged.
* Swipe (Cat): Percent of weapon damage done reduced from 260% to 250%.

Overall for a ulduar/naxx25 geared kitty, you'll see about 150 dps decrease. The nerf is more noticeable for lowly geared druids in naxx-10/heroics gear.

Edit with new gemming rule.

Cat dps flowchart (another one)

Fun flowchart similar to Aus's, but less awesome, depending on who you ask.

1/8/10: Updated with a dps spec that maximizes dps.

After much discussion, it is best to gem your gear for armor penetration before agility since hitting the soft cap makes agility kinda useless.
Haste is another good stat for feral kitties, use Agility/haste orange gems over agility/crit gems in yellow slots. Unless you need hit, then use Agility/hit.

For blue slots, use an armor pen/stm gem(puissant) or use a nightmare tear(+10 all stats).