There are full navigation and routing programs available for S60 and Windows Mobile that I use for major trips, but for quick positioning and some trips I just fire up the Google Maps for Mobile application on these devices. Google just released an update that adds transit directions to these mobile operating systems. They previously launched support for BlackBerry and Java-based devices so this expands their mobile offerings, with just the iPhone and Palm OS left to upgrade.
The new transit directions functionality gives you routing for public transportation systems in select markets. I haven't yet tried it out in the Seattle area, but we have a fairly new bus and rail system so I am not confident there will be much for our area and imagine support will be there for areas like Washington, D.C., L.A, New York, and other large metropolitan areas. Simply go to google.com/gmm in your mobile browser to download the latest Google Maps for Mobile client. Thanks to Nokia Conversations for the heads-up on this release.
UPDATE: I installed this on my Nokia E71-2 and it does support local bus routing here in downtown Seattle. The program even tells you (and shows you with an icon) that you need to walk to a specific bus stop to catch the bus, with departure and arrival times. It didn't calculate a transit trip from Seattle to Tacoma though so I need to keep exploring how much is supported. There are Sounder trains and Sound Transit buses from Seattle to Tacoma and hopefully these will be added in the future. Still it is a nice feature to have downtown and pretty amazing that they integrated it all into a free client application.
Have you tried it yet on your device and if so, what are your experiences?