Stealing from Youtube, iFilm, etc.

How do you take a file off one of them embedded movie sites?
Either one of two things will happen when I grab it from cache. It will be present as a file with an odd extension, but will be whole, that won't function properly in any movie viewing tool OR, it will download a movie file that is 40-140 bytes large, and will require me to connect to watch it (streaming.) Is there a way to take all the streamed shit for yourself? And does anyone know what the oddly extended (usually .tmp but not always) files actually are and what codec plays them?

I will gladly chuggle your e-penis!  So big!

Seriously, thanks! I was actually about to post something about this in the Questionable FireFox Extensions thread.

I'm not very knowledgeable about php.  Is there any way I could save this as some sort of stand-alone application on my PC, before it gets too popular and the site gets taken down by YouTube?  My guess is "no." 

The LJ Image Viewer php site from POE is still up and running, and I'm surprised it wasn't ripped down months ago by LiveJournal.  Also, I guess if they really wanted to, a few slight changes on YouTube's part could make even a static, stand alone application obsolete just as easily.

Again, thanks >>5!