As seen travelling to and from work:
1. A couple in the car arguing about something.
2. Another couple - both holding hands over the gear :-)
3. A single man in the car - tapping his fingers to the music or talking over the handsfree.
4. A big shot in a swanky car with driver - on the laptop or talking on blackberry
5. A call center cab taking people back home- all dozing in the car
6. A call center cab with only driver - talking over the mobile and driving rash
7. A parent with a bored kid strapped in the front seat.
8. A busy body eating an apple/sandwich at the signal-probably having skipped a meal?
9. A confident lady driving a cool red Skoda Octavia (imagine me drooling over the car)
10. Finally, me me - sitting in a bus and observing all these and letting my imagination run wild - while my subjects are unaware ;-p
Observe anything else? Feel free to add in comments...