there is a pretty cool gadget on photojojo.com. it is an attachment that allows you to take street photos relatively unnoticed--you hold the camera as usual, but a little mirror is actually taking the photo from the side. that is a poor explanation, but you can check it out on the website. i think it's called 'spy lens' or something similar.
What a great thread. Made me realize I haven't done any street photography since starting this project. Here's one I did the day I started but didn't choose to use it:
Here's one of mine that I enjoyed taking: