Just to chime in and hopefully help some of the new-to-caching folks, I've got some tutorials on using an Axim for GeoCaching up at
http://th4tguy.com/nav/ . I'm still working on fleshing them out.
Right now, the most complete ones that will get you up and running are:
Using GeoCaching.com for a quick starter on finding and getting cache information,
Using CacheMate to navigate to caches and log finds,
and
GPX versus LOC for details on why to register CacheMate and at GC.com.
If you already have TomTom, I'm currently working on
Custom POIs in TomTom, which will detail how to use GPX Spinner and gpsbabel on PQs from GC.com to show caches on your maps as POIs with different icons for each cache type.
So far, I'm liking the use of GC.com and CM for actual caching. I just got TomTom custom POIs set up, which helps for navigation and browsing nearby caches while out and about. I've tried BeeLine and BCN, but I'm sticking with CM for now. I just heard about Smcache, but have yet to try it.
I'm using:
Dell Axim X50v PocketPC PDA
DeLorme Earthmate BlueLogger BT GPSr
Gomadic Window PDA Mount
and a generic clear Axim case (it's small, offers some pretection from the elements, and was cheap)
TomTom 5.21
CacheMate 1.2.0