There are a few useful raid addons that most people use to help with boss fights, record DPS (For E-cred) and that will show you what drops from what. Here are a few examples.
Deadly Boss Mods - This is a must for raiders as it has a number of uses, the main one is that during boss fights it will warn you of things like Lokens AoE Nova attack, or Archivons Enrage.
Recount - Used to record Damage, Healing, Deaths and DPS of you and your party, ranking from highest to lowest
Atlasloot - Will give you lists of the gear that drops from every dungeon in the game from Deadmines to Ulduar and everything in between.
These are just a few addons I use to, please tell me some of your favorite raiding, and even non-raiding addons