I don't normally worry about it when soloing or 5-manning (soloing because I use ZOMGBuffs for auto-self-buffing, 5-mans because I can pay attention to the 1-2 buffs that don't come from me ). When I'm in a 10-man or 25-man raid, however, I use an addon called XRS (X Raid Status). Mine is set up to watch Int, Fort, and Spirit buffs, Well Fed, Kings, Wisdom, and Might, Soulstone, and a couple others I can't think of. It also watches AFK's, In Zone, Raid Mana and Raid Health (to help when knowing when everybody's full health/mana before starting a boss fight).