If you have the pleasure of owning a macbook with a built in isight and want to make some small movies for your blog or you tube straight from your isight – give quicktime broadcaster a go!
Its free and produces pretty nifty movies you can also stream them to a external client somewere!!!!
http://www.apple.com/quicktime/broadcaster/
or for a quick movie without streaming and options simply use photo booth in movie mode – which is bundled with most macs!!! just hit the record button and the movies appear in your pictues/photobooth directory