I'm using my PalmOne Zire72 with a Holux GR-231 BT GPSr and Mapopolis auto-routing/mapping software. Great combo for USA and Canada, and they also sell maps for UK/Europe.

The GPSr was US$99 or so, ditto for the Mapopolis maps (though I now know how to crack the freebie maps to full functionalitiy..). The only (trivial) complaint I might have is that Mapopolis is ever so slightly PocketPC-centric, and doesn't "live" the PalmOS paradigm as well as it could as a result. But on an "extended input area" Palm unit (T3), much of that complaint would vanish.

Cheers!