Ever Google-hacked a webcam? You can use Google to find network webcams, and many of them do not require a password to view.
Here are a few search strings you can use to find webcams on the net:
Axis CamerasCanon CamerasMOBOTIX CamerasJVC CamerasFlexWatch CamerasPanasonic Cameras
Toshiba Cameras
Sony Cameras
WebcamXP Software
Though I've called these "hacks" they are really just carefully crafted search strings devised to locate the text that these specific cameras use on their internal webcam pages.