Just a curious question how many codices do you have (and which ones)?
I have 2 and it's the Orks' one and Tyranids' one...I wanna get them all to see what are the diffrences of the armies and the fluff and the advantages/disavantages of all the armies but for now I'll stick to the ones I have...here in Quebec (Canada) they cost bewteen 15$-30$, depends like the Necrons' one is 30$ and the DeamonHunters is 15$...as for the 2 I got they cost 20$ each...dunno why they aren't the same price...

Old Imperial Guard, current Eldar, Chaos Space Marines, Tau and Necrons.

Cityfight, Daemonhunters, Tau, Chaos Space Marines, Old Chaos Space Marines, Assassins, and Chapter Approved 2003.

Daemonhunters , chaos , blood angels and dark angels.

So far I have all the current codices for the races from this ed, this includes the older IG, CSM ones. I also have the Angels Of Death codex from last ed, as well as all the Imperial Armour books.

I collect them all ^_^

Got all 2nd edition, all 3rd edition, 4 Liber Chaotica, Infantryman's Uplifting Primer...
My, fluff is expensive these days :-(

Chaos Space Marines, Space Marines, New and Old Imerial Guard, Tau, Space Wolves, Chapter Approved 03 and Necrons.

I have Daemonhunters, Dark Eldar, Necrons, Tau, Chaos and Imperial Guard

I have Tau, Necrons, Chaos Space Marines, EoT, and Space Marines, so in total, 5.

Necrons, Chaos, Tau, and Eldar (some where...) for fantasy I got Dark Elves and Skaven, though thinking about getting Tomb Kings soon.

Only Tau and Eye of Terror, I'm afraid - though I'm giving some serious thought to picking up Codex: Space Marine just on principle.

Know thy enemy...

assassins, sm, dark eldar and imp guard

csm and dwarves

Wow! Everyone like has the Necrons one...(it's the new trend..lol) it's gonna be my next one it think or after I expand more my army :D

Space Marines, Index Astartes II (has the black templars codex), Deamon Hunters, Imperial Guard.

I plan on getting the Necrons codex too, but only because it has a lot of encounters involving Sisters of Battle.

Every new one + some old ones.

new and old imperial guard, space wolves, dwarves, orcs and goblins, high elves, hordes of chaos, imperial infantryman's uplifting primer.

Well, you asked:
Space Marines
Blood Angels
Imperial Guard (new)
Daemonhunters
Tau
Orks
Necron
Eldar
Tyranid
Eye of Terror
Armageddon

Know thy enemies...

I have none (Eep!) but these I have read thoroughly through many times:

Orks
Space Marines
Dark Angels
Blood Angels
Space Wolves
Tau
Chaos Space Marines
Imperial Guard
Tyranids
Necrons
Witch Hunters
Eldar
Dark Eldar
Daemonhunters
Armageddon
Eye of Terror
Chapter Approved (All)
Index Astardes (All)
Astardes Sketchbook
Inquisitional Sketchbook
Liber Chaotica (Tzeench, Nurgle, Slaanesh)
The Battle for Armageddon
The Gothic and the Eldritch

Wow. I still need both "The Art Of" books, and that's about it. Wow again.

In no particular order

Old Chaos
Space Marines
Space Wolves
Dark Angels
"Armour geddem"
Eldar
Old Imperial Guard
Nid
Ork
Cityfight
Blood Angels
Assasins

And Tomb Kings

I've got Necrons and Dark Angels <:)

Space Marines-
Space Wolves-
Imperial Guard-

I am thinking of buying the Demonhunter Codex, so I can use them with my Cadians. I have also thought about buying the Tau just so I can read all the fluff on them. Thats half the reason you buy this stuff, right?

I got

Space Marines
Armageddon
Daemonhunters
& soon to be Imperial guard. My guard army is a very long long work in progress (Vallhallen Ice Warriors)

I have (takes a deep breath)
Space marines, Dark angels, space wolves, chaos space marines, Dark Eldar, Eldar, Craftworld Eldar, Tau, Necrons, Imperial guard, Tyrannids, and Orks

I have:

CSM (Old and New)
Space Marine
Imperial Guard (old)
Eldar
Dark Eldar
Necron
Ork

And i also have the Vampire Counts one for Fantasy.

Next thing will propably be the new IG.