After lasts night raid, I think that some people don't have some/any of the addons that help with raiding. Here's a list of the ones I use.

BigWigs: This a boss mod, which makes boss encounters much easier to handle. A must have for raiding.

http://wow.curse.com/downloads/details/3299/

Omen: Shows players threat, so players can easily see how much aggro they have on a mob and more importantly make it easier to not overaggro on the MT/OT. Must have for raiding.

http://wow.curse.com/downloads/details/9101/

Natur EnemyCastBar: Shows how long until debuffs wear off, shows respawn times for kara etc. Very useful when re-shackling targets.

http://wow.curse.com/downloads/details/2786/

Decursive: A box lights up when a player in the raid has a debuff that you can cure, and you just one-click the box and it automatically cures them (not too sure how this works as I'm warrior, but I know it makes curing a hell of a lot easier).

http://wow.curse.com/downloads/details/3011/

CT Raid Assist: A collection of mods that just generally helps. LOL. It does many things, don't ask stupid questions

http://www.ctmod.net/downloads/

Taunt Buddy This is awesome, only needed for tanks, it shouts out when taunt is resisted. It's just a useful mod to have for tanks when clearing trash etc.

http://wow.curse.com/downloads/details/2060/

Maybe you guys have all these? or you have more useful addons? Feel free to add more.