Microsoft's new ClearFlow system looks pretty nifty:
http://www.nytimes.com/2008/04/10/te...gy/10maps.html

Is there any way that we PalmOS users can access it (e.g., via Blazer)? Or perhaps an enterprising software developer?

The potential advantage over GoogleMaps is that ClearFlow includes sidestreets and predictive algorithms for minimizing time in traffic.