With the launch of Motorola's Droid, Google has also launched Google Maps Navigation (Beta) as a free turn-by-turn GPS navigation as part of Google Maps Mobile for Android. However, initially Google Maps Navigation was available for the U.S. only, and even if it became part of Google Maps Mobile, it only worked in selected countries (after the U.S. the UK and other countries followed). Now it looks like Google has rolled-out the next wave of supported countries. For instance Germany, Austria and Switzerland (DACH) seems to be supported as well now (and it's expectable that other countries are now supported also), giving Android users a free turn-by-turn GPS navigation solution.
Using Google services over a phone's data connection brings important benefits to GPS navigation users, like using Google search (typed or spoken) to enter your destination; fresh map, business and traffic data and - for sure - satellite and Street View imagery along your route. Nevertheless, since Google Maps Navigation is an off-board navigation system, users better have a data plan in place and it's advices that it's not heavily used in international roaming.
While Google initially supported Android 2.0 or later only, afterward it released a Google Maps Mobile version which also supported Google Maps Navigation on Android 1.6 or higher devices, therefore Google Maps Navigation should be available for most of today's available and used Android smartphones.
UPDATE: Google has just announced on its blog, that Google Maps Navigation is now available in Austria, Belgium, Canada, Denmark, France, Germany, Italy, the Netherlands, Portugal, Spain and Switzerland.
Cheers ~ Arne