You could start with the usual suspects, CBS, ESPN etc. I think you will need to test with rule tracing to get the biggest hitters. We also squash a lot of this on the routers, by not giving this traffic priority, so it makes it painful for the user.
If for some reason this ruleset doesn't work as expected, let us know what sites you are able to access the video on, what browser is being used and a rule trace if possible. Testing with IE, Chrome and Firefox has been blocking all of the videos for me.