ViDL allows you to simply paste a website URL, which the app will then scan for videos. You can select the ones you want to download and even have the option to download the audio only.
ViDL can also install a Safari browser extension as well as a bookmarklet for other browsers. To download a video from a website, simply click the button in the browser window.
ViDL uses youtube-dl in the background. If you want more control, try youtube-dl without ViDL: