Two websites that do this for you:
http://www.clipconverter.cc (do not use this site – it works but it has some ads that are a scam)
It used to be that to download a flash video on your mac you needed to get a video downloader for safari, but now the best way seems to be to go a webpage that will do the hard work for you. It will convert the movie from a flash file to a normal (.mov) file and create a link and then you can download the file directly from safari. Here’s how to do it:
1. Go to the site that has the video that you want to download (e.g. http://videowebsite.com/). Then go to the page with your movie.
2. Copy the URL of the page the movie you want is on. (It will be something weird, probably like this: http://website.com/video389fhw4r0) To copy the address, click in the safari address bar, double click the address to select it, then press Apple-C to copy it.
3. Go to one of the websites above and, in the little box, paste (Apple-V) the URL.
4. Press ‘Download, and a number of formats will appear. Generally the best is the biggest format.
5. Select the format you want and press ‘download’.
6. It will download into your safari downloads folder.