here's something I made for myself a while ago, it should be a starting point, at least better than nothing (it's up to you to figure out how to plug it into NNF though ^^)..

%
	$return = preg_replace (array(
		'/\[VIDEO\]http(.+?)youtube(.+?)\/watch\?v=(...........)(.*?)\[\/VIDEO\]/si',
		'/\[VIDEO\]http(.+?)youtu\.be\/(...........)(.*?)\[\/VIDEO\]/si',
		'/\[VIDEO\](.+?)vimeo\.com\/([0-9]+?)\[\/VIDEO\]/si',
		'/\[VIDEO\](.+?)screen\.yahoo\.com\/(.+?)-([0-9]+?)\.html\[\/VIDEO\]/si',
		'/\[VIDEO\](.+?)video\.google\.com\/videoplay\?docid=(.+?)&(.+?)\[\/VIDEO\]/si',
	), array(
		'<object width=100% height=300><param name=movie value=http://www.youtube-nocookie.com/v/\3?version=3&amp;hl=en_US&amp;rel=0 /><param name=allowFullScreen value=true /><param name="wmode" value=transparent /><param name=allowscriptaccess value=always /><embed src=http://www.youtube-nocookie.com/v/\3?version=3&amp;hl=en_US&amp;rel=0 type=application/x-shockwave-flash width=100% height=300 allowscriptaccess=always allowfullscreen=true wmode=transparent></embed></object>',
		'<object width=100% height=300><param name=movie value=http://www.youtube-nocookie.com/v/\2?version=3&amp;hl=en_US&amp;rel=0 /><param name=allowFullScreen value=true /><param name="wmode" value=transparent /><param name=allowscriptaccess value=always /><embed src=http://www.youtube-nocookie.com/v/\2?version=3&amp;hl=en_US&amp;rel=0 type=application/x-shockwave-flash width=100% height=300 allowscriptaccess=always allowfullscreen=true wmode=transparent></embed></object>',
		'<iframe src="http://player.vimeo.com/video/\2?title=1&amp;byline=1" width="100%" height="300" webkitAllowFullScreen mozallowfullscreen allowFullScreen></iframe>',
		'<iframe frameborder="0" width="100%" height="300" src="http://d.yimg.com/nl/vyc/site/player.html#vid=\3&lang=en-US"></iframe>',
		'<embed src=http://video.google.com/googleplayer.swf?docid=\2&hl=en&fs=true style=width:100%;height:300px allowFullScreen=true allowScriptAccess=always type=application/x-shockwave-flash></embed>',
	), $return);
%

I hope this shows up correctly :/ Otherwise feel free to edit/delete.

Yes, you can break a forum by posting huge images. But when it comes to videos, personally I actually prefer the video still thumbnail than a cryptic link which automatically plays the video when visiting it, I consider that less annoying... anyway, if anyone wanted to crap over a NNF installation, there is nothing stopping them, so the reasons people don't do it aren't technical ones. Just a thought or something :)

Oh, I forgot to mention, that the above snippet expects the links inside of [video] tags -- you might want to remove those bits from the beginning and end depending on your use.

Cheers :) I'm not that good with regexes, so there's likely to be room for improvement, but it worked nicely for me so far. By now I kinda prefer that over pasting embed codes, even in my own pages, because it allows for to tweaking all embed codes in one fell swoop. I'll probably never "need" that, but it just feels good haha ^^