VideoBooth

Video Booth is a fun application that you can use to take funny photos and videoclips with your webcam. It includes special effects for both the photos as well as the videos, to help you find the perfect finishing touch. Once you've achieved your desired results, you can publish them to your favorite social network.

The program is very similar to Apple's official Photo Booth application, so anyone who has played with that before will know what their options are. However, this tool is very easy to use, so you'll be fine even if you don't have experience with a similar program.