Megavideo is alright, but nothing more. After 72 minutes of video, you have to wait a while before watching more, which gets REALLY annoying when I'm right in the middle of watching something. Connection problems all the time as well, but overall it's not bad, I suppose.
Then there's shit like imeem which is fucking terrible, takes about an hour and a half to stream twenty minutes of video most of the time, whereas on any other site the same sized video will load in minutes. Site looks horrible, the player sucks, and it's SLOW.
There's a fuck load of others, I know, but those are the only two which immediately come to mind. Besides, most are just really unused and have too many flaws. There really is no good alternative to YouTube, which is a real shame since YouTube always sucked and is just declining into even larger fail.