One of the raid add-ons that I like to use is BigWigs which provides warnings of special attacks by raid bosses, proximity warnings, and phase changes in the fight where you need to start doing something different.

Up until this month, the old BigWigs proximity warning was nothing more then a list of people who are closer then "X yards" away from you. On certain boss fights, you have to be a minimum distance away from other raid members to prevent taking splash damage when the boss puts a debuff on a fellow raid member.

This month, they've updated the proximity display to be more graphical. Now it looks like a little radar screen with colored dots (by class) of anyone near you. You can look at it and figure out whether people are crowding you to the front, from behind or left/right.