Ubuntu Tech Notes
The webcam is an USB mdel, Z-Star ZC0305.
With Skype (Beta) 184.108.40.206, I was unable to see or let other users see my video: the test screen (Skype options) remained black, while in a conversation my video window did not even appear.
The video instead appeared correctly in Cheese.
I was able to solve the problem with Skype using the solution given in this Ubuntu forum: run Skype using the following command
env LD_PRELOAD=/usr/lib/libv4l/v4l1compat.so skype
libv4l must of course be installed.
This solution has not been tested on other machines or with different software configuration, but I hope it is useful for other users as well.