A small application, called "macam", is a real help in such situations. It has included the USB drivers for almost any webcam, from almost any manufacturer. And, it is capable of taking pictures and recording, with many configurable settings. And it's really simple to use.
Download from here: http://www.4shared.com/file/235587242/5228325f/macam092.html.
To avoid problems of any kind (errors, conflicts, kernel panics, etc) and for a list of webcams which should work or which should not work, please visit the official site: http://webcam-osx.sourceforge.net/index.html