If you’re a cool web user you might be interested in this: I came across a GreaseMonkey script the other day by Josh Kinberg which makes it easy to download YouTube videos.
Pretty awesome but it seems broken now, either with Firefox 3 incompatibilities of some sort or a change to YouTube’s page layout (could be both – different rendering sent to the new browser..)
Anyway, I made some minor edits to it to make it compatible with whatever’s causing this problem and added a link to the swf url, which you should be able to use if your forum supports (or allows) [flash] tags.
[Edit_080709]
If you happen to be (or know someone who is) a forum admin, you can define your own BBtag like so (the example is for PHPbb but I’m sure an equivalent can be reproduced in any forum that supports custom BBcodes):
[fl]{URL}[/fl]
Becomes:
<embed src="{URL}" type="application/x-shockwave-flash" allowfullscreen="true" width="425" height="344">