There are a number of addons that provide a lot of raid tools related to information about the encounter and communication. The #1 tool used is CT_RaidAssist (CTRA). Personally I'm currently using ORA2 because it uses a lower overhead (but the messaging is still compatible with CTRA). Unlike CTRA it does not provide its own raid frames (the display of the members of the raid) but will work together with a number of other frames including Blizzard's built in frame. For Boss Mods I use BigWigs (ace), but another option that I've looked at (and that also provides battleground information is Vendetta).

Blizzard's raid frames are unvieldy and don't provide very good main-tank support (I like seeing who the main tank is and, more importantly, which tank is targetting which opponent). I'm currently using EasyRaid.

While other mods such as Vendetta and Sorren's Timers provide BG functionality I've come to depend on AlarBGHelper to provide me with timers as well as macros to announce "incoming at xxx" as well as the timers.