http://www.apple.com/trailers/
http://starwars.apple.com/ep2/forbidden/

Can someone tell me how to find the .mov file on this site (medium, say):

http://starwars.apple.com/ep2/forbidden/forbiddenlove_md.html

Do you use "View Source". Then how to save it to HD? Use: "Save link as" ?
If so, I get a file of 10KB. When trying to open in K-M it doesn't work.

you would find the URL of the .mov file in the source (perhaps by hitting Ctrl+F and searching on '.mov' ), then copy and paste it into the URL field of k-meleon (or some other downloading software) and hit 'enter'.

That's the logical way of doing it, but apparently some sites don't want you to save it. e.g. I got the .mov file -- try saving this -- is it around 15 MB ??? I got it to be 10KB! :
http://starwars.apple.com/ep2/forbidden/img/ctp_a_320.mov

Anyway this seems to work for QT 5.02:

In Plug-in settings makes sure "Save movies in disk cache" is ticked then after download move (and rename) the file from the Cache folder to your own folder.

As K-M doesn't do extensions in the Cache folder (why not?) you have to add "mov" as the extension.

I've noticed that a plugtmp folder has been created in my gxxxxxxx .slt folder (along with chrome and cache). Dunno what this is for and if it's been done by Quicktime or K-M.

ah, i see what you mean. i don't know much about streaming media formats... maybe quicktime is actually required to get more than the first little chunk of file? hopefully somebody can explain it.

Some files can't be downloaded directly. Mostly the ones directly served over apple.com. Those are hosted at akami and those files seems just to be another redirecter to the real file. You can't download those via a browser...
They are "real" streaming files...like when you try to download a realmedia files, what is being streamed. You just get a small few KB big files as well...
Look for unoffical sites, that host the trailer for download.