The venerable free medical calculator MedCalc for Palm now has a Windows Mobile version as well. MedCalc was my PDA calculator of choice during residency but since I switched to Pocket PC (now called Windows Mobile), I had to use Archimedes instead.
It is nice to see that MedCalc is still alive and getting updated. I have assembled a long list of free PDA software here: Free Medical Programs for Windows Mobile / Pocket PC.
Image source: MedCalc.