What webcam apps are available and how to check if your webcam is working?
Cheese 
Cheese uses your webcam to take photos and videos, applies fancy special effects and lets you share the fun with others. It was written as part of Google's 2007 Summer of Code lead by daniel g. siegel and mentored by Raphaël Slinckx. Under the hood, Cheese uses GStreamer to apply fancy effects to photos and videos. With Cheese it is easy to take photos of you, your friends, pets or whatever you want and share them with others.
VLC can be used for the given purpose.
Media - Open capture device...
Click drop-down menu for Device selection - Video device name.
When something like/dev/video0 appears, just click Enter.
Then Play.
One can also launch directly the VLC webcam.
Save the playlist as the VLC webcam is running. Media - Save playlist to file... (e.g. save as vlc-webcam.xspf playlist file). Starting that playlist file in VLC will start the webcam.
Then one may create a desktop file for the same purpose; it should be similar to this:
[Desktop Entry]
Name=VLC Webcam
Comment=Webcam vlc
Exec=vlc /path/to/vlc-webcam.xspf
Icon=/add/some/image/png/file.png
Terminal=false
Type=Application
StartupNotify=true
Categories=AudioVideo;Player;Recorder;
Make it executable. If you copy that into /usr/share/applications it will be searched and launched directly as any other application. In Synapse:
Mousetrap
What is MouseTrap?
Mousetrap is a standalone GNOME application that allows users with physical impairments to move a mouse cursor. It uses a webcam to track the motion of any object visible by the camera and moves the mouse cursor according to the path of the tracked object (a user's head, for example). Distributed with software that allows accessible mouse clicking, MouseTrap will give most physically impaired users access to the full functionality of a mouse. Our ultimate goal is to have a usable, stable solution that allows users to control their cursors just as well as someone using a mouse. MouseTrap is written in Python, based on the OpenCV library and uses image processing to translate the user's head movements into mouse events (movements, clicks) which allow users to interact with the different desktops managers and applications.
How does it work?
Youtube demo video
http://www.youtube.com/profile?user=flaper87#grid/uploads