Mediquations Medical Calculator [$4.99, App Store] provides a set of frequently used medical equations from your iPhone. Over 40 common equations are supported, including the MDRD, Free Water Deficit, and Fractional Excretion of Sodium.
The launch of the iPhone app store has opened the market up to medical applications which have flourished on the Palm platform for years. The free Epocrates Rx [App Store] was the highest profile and perhaps most requested medical application that launched with the App Store. Other potentially useful apps for medical professionals include:
Netter's Advanced Head and Neck Flash Cards $39.99)
Netter's Musculoskeletal Flash Cards ($39.99)
Medical Calculator (Free)
OB Patient Tracker ($14.99)