This thing is awesome!
I always try to avoid installing dodgy software and avoid bloating up my browser with add-ons by first checking if there is a bookmarklet that will do the job.
Here is a great one. Even though it’s porn functionality is not well advertised, the bookmarklet from deturl.com is surprisingly capable of downloading videos from a huge number of porn sites.
So far I have used it to download video from xvideos, xxxbunker, tube8, youporn, xhamster, deviantclip, hardsextube, stileproject, redtube, pornhub, tnaflix, eporner, fftube, tjoob, spankwire, slutload, faptv, youjizz, dailymotion, vimeo, AND MANY MORE.
Oh, BTW, it works on YouTube and Facebook also ;-)
(Bonus tip: The best video player there is for playing all file formats is the free and open source VLC PLayer.)