This addon will add raid icons (Skull, Star etc) to the standard Blizzard raid frames. For some reason Blizzard didn't include this in the code which makes it hard to use the raid frames in combination with, for example, boss mods that puts raid icons on raid members.
Icons will be shown on party members if the "Use Raid-Style Party Frames" is selected and on all raid members. Currently the mini-frames (used for pets and targets) aren't supported.
If you like this addon, you might also want to take a look at Blizzard Raid Frames - Indicators - Which will give you timers on the raid frames for any buffs/debuffs you want to watch.
Configuration is simple enough and can be found on the addon config pane or by typing "/RaidFrameIcons config":
Icon Size - Size of the icons
Icon Position - Position of the icons relative to the unit frames
Enable - Enables/Disables the addon