I'm using Bunchofbars to check what the raid is targeting, when the mainassist is down.
It's a minimalist raidframes-addon, which shows the raidsymbols of everyones target (or if there is no raidsymbol, its a blue little square besides the healthbar when this person has the same target as me).
Quite handy, i love the addon, because it's small and shows only the information i need (as a rogue). No extra ToT-frames for 25 people, which take some space.
http://www.wowace.com/wiki/BunchOfBars