Making this thread for all you boxers to use, just a thread that points to all the others so to speak, since there are a ton of diff combinations and a ton of diff tactics, I thought it would be best to keep a list for much easier use. I'll keep updating the top post with links to peoples strategies. Please use the following template for clarity:

Note: This is for heroic instances and raid(normal and heroic) instances only.

Code:
Instance: <Name>
Box: <your box set up> (ex. "Prot Paladin, 4x Ele shaman")
Gear level: <pre-heroic blues/greens(70 epics count as these), heroic blues/epics, heroic epics or full epic>
Difficulty: <smooth(cakewalk)/easy(some deaths, no wipes)/normal(some wipes)/hard(learning curve+wiping fests)/Problematic(Serious issues with certain bosses and multiboxing)
Guide: <easy to read and not too long walkthrough of the instances, preferably including how to handle trash mobs, specifically if they are problematic. And a rundown per boss. Keep to the point of the instance and don't start chit chatting too much about unrelated stuff!>

<Below post possible unrelated stuff or just some remarks!>
Utgarde Keep
4x elemental shaman [Kaynin]

The Nexus
General Ranged DPS tactics that make things easier[Ss2]

Azjol-Nerub
4x elemental shaman [Kaynin]

Ahn'Kahet: The Old Kingdom
Protection Pally, 3 frost mages, 1 resto druid 5 box [Pinotnoir]

Drak'Tharon Keep
Protection Pally, 3 arcane mages, 1 disc/holy priest 5 box [Zha]

The Violet Hold
4x elemental shaman, info on three bosses [Kaynin]

Gundrak
4x elemental shaman [Ellay]
Protection Pally, x3 Arcane Mages, x1 Disc/Holy Priest 5 box [Zha]

Ulduar: Halls of Stone

Utgarde Pinnacle
3x elemental shaman + 1x resto shaman + prot paladin 5-box [Mrmcgee21]

Ulduar: Halls of Lightning
Protecting Pally, x3 Arcane Mages, x1 Disc/Holy Priest 5 box [Zha]

The Oculus
DK + 4x elemental shaman [Alemi]

(Normal) 4x elemental shaman, warrior tank [Tdog] Boss 1, Boss 2

The Culling of Stratholme
4x elemental shaman [Kaynin]

Naxxramas (normal)
4x elemental shaman, Spiderwing [Kaynin]
4x elemental shaman, Death Knight Wing, Plague Wing and Abomination Wing [Ellay]

Naxxramas (heroic)

The Eye of Eternity (normal)

The Eye of Eternity (heroic)

The Obsidian Sanctum (normal)
4x elemental shaman [Kaynin]

The Obsidian Sanctum (heroic)

Vault of Archavon (normal)
4x elemental shaman [Kaynin]

Vault of Archavon (heroic)