Since recently, I have been using Opera only, and I like it a lot. But one of its shortcomings is the unavailability of extensions, which would help in my situation.
I don't want to open a website everytime I download a video, so I looked on the web, and apparently they say you can run Greasemonkey scripts on Opera. THere are also bookmarklets.

So my question, what's the best way to download videos from inside opera?