Maybe this is obvious, but it was new to me. :)
Today I skimmed through the jroller.com homepage and found an article on Valerio Schiavoni's blog about revision control systems. He embedded a link to a video on YouTube showing Linus Torvalds giving a speech at Google about git and why he thinks it's better than other revision/software control systems.
When I started to watch I realized I would not have time to watch it to the end. So I wanted to save it locally and watch it later, without having to be online again. So I googled for "download youtube videos" and the first three matches all pointed to one sort or other of special download tools.
Turns out you do not really need anything like that. By chance I found the completely downloaded video file in the
/tmp directory named something like FlashRItWZO. I tried some video on Google video, too, works fine as well. The files all start with "Flash" and are then followed by some random part.
You just have to wait until the whole video is buffered. You can then copy the file from the
/tmp directory to some more permanent location. On Linux mplayer happily plays them.
One caveat needs to be remembered however: If you want the whole video you must not seek through it while it is still streaming. Otherwise you will end up with just the parts you saw/that were buffered. On the other hand you can of course use this to only store a part of a longer video, in case you do not need the whole thing.