"António Jorge Gonçalves makes drawings of people sitting in subway trains in 10 cities around the world. He stays an average three weeks in each city, making around 300 drawings which seek to cover different times of the day and the different lines of the subway system.". (From the homepage.)
The user interface of this flash site might be a bit slow and makes it a bit difficult to see and really enjoy the work, but the drawings presented on the site are really quite stunning. Enjoy Subway Life.