My friend gZa emailed me this link to KeepVid, you can use it to download clips off YouTube (film trailers being one of my faves) then do what you want with them ie. burn them to DVD and play them on a proper TV / bigger screen.
I can see this being useful for work and play...
Also as a handy bonus the site will also convert .flv files to something you can actually watch via your desktop. I encountered .flv (Flash Video) files for the first time last week and spent half an hour trying to figure out how to watch them before i realised they couldn't be played through Macromedia Flash or WMV. In then end i uploaded the files to YouTube to watch them. The reason is that Flash Video is designed for streaming rather than watching like a WMV or MPEG file (correct me if i'm wrong).
However if you don't want to upload to YouTube or use KeepVid to convert them you can view .flv files using a number of standalone players. There's one on the KeepVid site and also the following player from Martijn de Visser (thanks for the link gZa).
Convert video files online (July 2008)