I hadn't done much with Google Video until someone sent me a link. I watched it in Firefox and said "hmmm, I want to save this." Given that I had already waited 10 minutes for it to download, I didn't want to download it again. It turns out it was 40Mb. I figured "this file is in cache on my hard drive already somewhere, all I have to do is find it."
I ran
Code:
lsof | grep -i flash | less
. That showed me that the flash plugin was opening a file named /private/var/tmp/folders.5059/TemporaryItemsFlashTmp0000.
I renamed that file to 'foo.flv' and I had my file. I didn't have to download it a second time. I suppose you might have a bunch of files in your cache, but this was the only one I had.