Built in clock app – stopwatch for long exposures.
Holders – Manage film holders, note details, geotag exposure, audio notation
Massive Dev Chart developing table app – More developer and film combinations than I may ever use, customizable. Steps through development
Digital Depth of field calculator – Hyperfocal distance and diffraction calculation
The Photographers Ephemeris – sunlight/moonlight visualization
Hipstamatic – Gives an idea of what a black and white version of the scene looks like. I like to use the tin type filter.