I used to keep my dive log on my pocket pc/phone and transfer it to my computer when I got home. That went away when I got a dive computer.
However, diving WITH one is completly different. I can think of NO reason why I would want to take a $600+ phone/palm diving with me? Diving is a great way to get AWAY from it
EDIT:
reactive, what pocket PC do you have? I have the UT StarCom 6700 which used Windows Mobile. It has excel spreadsheet, (which is what I use to log my dives) and can be transfered to a desktop, or vice versa.
If you dont liek Excel, here are a couple programs for pocket PCs:
Dive Assistant - Pocket PC Edition 2005 / free download
Diving Log for Pocket PC - Logbook software for scuba divers.
Download SharkPoint for PocketPC, the scuba dive log 1.5.1.05 Free Trial - SharkPoint for PocketPC, the scuba dive log