These are just some of the sketches I make everyday on way to and from work, I started in 2005 and I seem to have become a bit addicted now. I always position myself in a place where I can get a good view and not become a nuance to the person I am sketching.
Sometimes people still see me, have a look at it and have requested for it. When I like it so much I tell them that I can't tear it out for them but will be willing to e-mail it to them if they gave me their mail address.
Some I never finish, it depends on the length of the journey too.
I noramally use pens (black biro) and Tomboy art brush pen N75 for the shades and tones. http://www.hi5.com/friend/profile/displayJournal.do?ownerId=23382643 -this link will take you to a full months journal.
Keep sketching and don't give up. For real inspiration on the whole beauty of sketching and for encouragement see http://www.wetcanvas.com/forums/showthread.php?t=350853