I've been using Waze over the last couple of months (www.waze.com). The best way I can explain it is like wikipedia for maps. You drive the roads and then edit them on the website. If you run it everyday on the way to and from work then it can find optimial routes, mark traffic jams, police traps, accidents etc.
I've done my best to build out the maps on the north shore and they should be at a level where they would be useful to people (most major roads are built and the majority of suburbs/smaller roads).
The application is free and available on iPhone, android and windows mobile (blackberry coming soon). The more people that use the service the better it will become for everyone.




) that provides me voice prompt navigation. I understand any potential annoyances if you are the first to get it in your area, but with only a few 'wazers' the major roads are soon filled in.