Downie> is a video downloader for OS X. It supports at this moment over 1000 different sites. The full list may be viewed in Downie's preferences, under the Sites tab. With each update, we add several new sites as per your requests - just send us a link to a web page that doesn't work and we'll most likely add it in the next update. Downie supports HD video on YouTube, up to 4K. Need your video in MP4 for iTunes? Or want just the audio track? No problem, Downie can handle this for you automatically. I respond to emails usually within 24 hours and often add support for requested sites in the next update. Don't wait weeks for new sites to be supported, or bugs to be fixed. Downie is updated about once a week with new features, sites supported.
Has extension that add a Downie button to Safari and Firefox that when clicked will search the current page and show videos on it. Click the play button and the video is downloaded. Works with Aviator, and Opera, but the extension install is not obvious.