The one I'm testing at the moment is called BBtracker (not surprisingly a BlackBerry application). Open source and in early stages of development at the moment so its not perfect but is a nice little App for anyone with a BlackBerry.
bbTracker - Trac
There are a lot of other freeware gps track logging apps for PPC's as well but haven't had chance to try to many yet.

I never thought about it much before but there are more uses for GPS units on a PDA. I'm hoping I get chance to try this one out over the weekend (don't think I could get Chris to agree to give me the day off tomorrow for "testing" purposes ).
Pocket mCaddy GPS **BETA** 0.41b Windows Mobile Pocket PC

I would like to find some free GPS navigation software for Symbian 9 S60 devices though (Nokia N73 specifically) so if anyone has any suggestions let me know. Doesn't need to be anything fancy but if it can tell me where I am and give me a rough idea of how to get to where I want to go it will be fine