If you've ever been to the Nürburgring, you must have seen Sabine Schmitz. She's an ex-professional race driver who now drives 1100 to 1200 laps every year in the Ring Taxi and runs a famous (infamous?) establishment in Nürburg (the Fuchsröhre).

According to various interviews, she was 6 months old when she first drove the Ring (albeit in the back seat of her father's car). She did her first lap behind the wheel when she was 17, without a driver's license in her mother's car. Of course, mother didn't know what Sabine was up to :-) When she was 19, she set the lap record in a Ford Sierra Cosworth (8'16").

If you want to know more about her, there's an interview that was broadcast on DSF on this site.
For those who want to know what a lap in the Ring Taxi feels like: there's a video right here.