Mercedes is introducing a feature called Search and Send to that will allow you to send Google and Yahoo! driving directions directly to your car's navigation system. How it works: you get driving directions from either source, and then hit a button labeled Send to Car. If you have a Tele-Aid subscription, when you get in your new Mercedes you can hit the "i" button, and the car will download the directions. Voila and giddyup.
You can even send directions from your PDA, or have someone else send directions to you while you're in the car. However, the unique identifier that gets the directions to your specific car and no one else's isn't spelled out. It also isn't clear if this is only for new cars, or if your 2005 CLK and your woeful sense of direction can ever benefit. The release says it will start off on the S, CL, and new C-Class, and be phased in across the range over time. It doesn't become available until September 5, but you can see a video of it here.