This module flashes suggested spells for all three DK specs. You can find *lots* more information on its website.
Bitten's SpellFlash modules replace Blizzard's default proc highlighting to flash the button you should press next to achieve maximum dps on a boss fight. Or if you are a tank, to maximize your survivability. For healers, they are just slightly smarter proc highlighters. Dps modules follow or are similar to priority schemes found in SimulationCraft and/or Icy Veins. Sometimes you have to be smarter than SpellFlash, e.g. when saving a cooldown for a specific boss mechanic, but in general following the recommendations will improve most people's performance.
Some modules have AoE modes. Check the descriptions of each rotation to see if one is available for the spec(s) you use.