StatCoach

Each secondary is shown as rating against the point where it starts losing value - blue under the line, gold past it. The tick marks the guide's haste target for Subtlety, and the NOW line says how much rating is left to reach it.

Your spec's priorities and live cap bars on the left, the enchant it wants in every slot in the middle. Click a row and a waypoint lands on the vendor who sells it. Hovering says whether your reputation is high enough to buy it yet.

Easy spot an upgrade item in backpack

Hover any combat stat and StatCoach shows your caps as live progress bars, right in the tooltip. Green = capped, red = work to do - against a +3 raid boss, with racials and talents counted.