Oboi here we go

Orks

Infantry
Each infantry health upgrade adds an additional 5 armor to the unit, which is represented with an xx/xx for default/upgraded.

Gretchin
Armor - lol
Penetration Values:
Knife - 10
Slugga - 10

Field Gretchin
A combination of standard Gretchin and Shootas, sharing stats with each.

Gretchin Swarm
Armor - The skin on their backs
Penetration Values:
Knife - 20
Slugga - 15

Boyz
Armor - 30/55 (w/ Scrap looted) (Normal)
Penetration Values:
Choppa - 45
Slugga - 15
Choppa (Nob Leader) - 75

Shoota Boyz
Armor - 30/45 (Normal)
Penetration Values:
Shoota - 35/40 (w/ Scrap looted)
Knife - 10
Rokkit Launcha - 170
Stikkbomb - 40

Stormboyz
Armor - 30/55 (w/ Scrap looted) (Normal)
Penetration Values:
Choppa - 45
Slugga - 15
Allahu Ackbar - 200

Deffgun Lootas
Armor - 30/45 (Normal)
Penetration Values:
Deffgun - 40/45 (w/ Scrap looted)
Sod off (melee) - 10

Tankbustas
Armor - 35/50 (Normal)
Penetration Values:
Rokkit Launcha - 170
Knife - 10

Nobz
Armor - 70/85 (Normal)
Penetration Values:
Choppa - 75
Frisbee axe - 125

Meganobz
Armor - 125/140 (w/ 'Arder Daddy research, not affected by infantry health) (Heavy)
Penetration Values:
Power Klaw - 125
Twin-linked Shoota - 50
Kombi Rokkit - 180

Vehicles & Structures
Ork vehicle armor is upgraded the same way as infantry, at +5 per upgrade. Gork and Mork have an upgrade which adds 50 armor.

Trukk
Armor - 125/140 front, 75/90 rear (Heavy)
Penetration Values:
Big Shoota - 40

Killa Kan
Armor - 110/125 (Heavy)
Penetration Values:
Rokkit Launcha - 180
Power Klaw - 80

Deff Dread
Armor - 160/175 (Heavy)
Penetration Values:
Power Klaw - 175

Deffkopta
Armor - 80/95 (Heavy)
Penetration Values:
Twin-linked Shoota - 60

Big Trakk
Armor - 175/190 front, 100/115 rear (Heavy)
Penetration Values:
Supa Kannon - 150
Artillery mode - 100
Mine - 125

Looted Tank
Armor - 170/185 front, 110/125 rear (Heavy)
Penetration Values:
Supa Kannon - 200
Heavy Bolter Sponson - 45
Garden Hose - Yes

Mad Dread
Armor - 180/195 (Heavy)
Penetration Values:
Drill - 200

Gorkanaut
Armor - 250/300 (Heavy)
Penetration Values:
Deffstorm Mega Shoota - 75
Rokkit Launcha - 225
Skorcha - 50
Twin-Linked Shoota - 50
Klaw of Gork - 300
Rokkit Fist - 300

Morkanaut
Armor - 250/300 (Heavy)
Penetration Values:
Kustom Mega Kannon - 300
Kustom Mega Blasta - 75
Rokkit Launcha - 225
Twin-linked Shoota - 50
Klaw - 300
Rokkit Fist - 300

Da Warkamp
Armor - 225/240 (Heavy)

Da Boyz Hut
Armor - 200/215 (Heavy)

Da Dakka Hut
Armor - 200/215 (Heavy)

Pile o' Gunz
Armor - 200/215 (Heavy)

Mek Shop
Armor - 200/215 (Heavy)

Mork n'Idol
Armor - 200/215 (Heavy)

Ork Hut
Armor - 100/115 (Heavy)

Waaagh Tower
Armor - 150/165 (Normal)
Penetration Values:
Big Shoota - 50

Big Shoota Turret
Armor - 100/115 (Heavy)
Penetration Values:
Big Shoota - 55

Listening Post
Armor - 70/90 (w/ fortified upgrade) (Normal)
Penetration Values:
Big Shoota - 55

Mine
Penetration Values:
Kaboom - 150

Heroes
Hero levels provide armor and penetration bonuses in addition to health, damage, regen, and speed. The specifics are:
Level 1 - +5 armor, +10% penetration
Level 2 - +10 armor, +15% penetration
Level 3 - +10 armor, +15% penetration
Level 4 - +15 armor, +20% penetration

The maximum added armor (40) is reflected in these values. Penetration is not because I'm lazy.

Warboss
Armor - 55/95 (Normal)
Penetration Values:
Bigass Klaw - 100

All abilities also have the same penetration.

Kommando Squad
Armor - 40/80 (Normal)
Penetration Values:
Shotgun - 60
Choppa - 45
Stun Grenade - 50

Mekboy
Armor - 85/125
Penetration Values:
Kustom Mega Blasta - 75
Power Klaw - 75
Scrap Turret - 45