Must have plug-in when there are lots of photos to process and little time: EditLab Pro.

Must have plug-ins for general workflow: Neat Image or Dfine to reduce noise in high ISO images; Focus Magic to improve images that are out of focus (and even those that aren't); PTLens to remove optical distortion from pictures; and Sharpener Pro for output sharpening.

Incredible plug-ins for creative enhancement: the Color Efex Pro plug-ins Brilliance/Warmth, Color Range Contrast, Tonal Contrast, Pro Contrast,Darken/Lighten Center, Dynamic Skin Softener, Classical Soft Focus,Graduated Filters, Bi-Color Filters, Graduated User-Defined Filters,Graduated Neutral Density, and Midnight; and the Mystical Tone Tint and Color plug-ins Darken Colors, Deepen Tones, Enriched Black, and Green Foliage.