It's almost impossible to find a decent AMV in YouTube unless you know the exact name of the video you're looking for, in which case you'd be able to get a higher quality version of the video elsewhere... animemusicvideos.org is full of trash too but at least it's easier to find the few gems there and the quality is infinitely better in most cases. It is the best AMV site I know of.
I just noticed madmovie.org is dead. Anyone know what happened to them? You might still be able to find their packs on torrent sites and such. Technically they're MADs not AMVs but who cares about the nationality of the person who made the video and other such details
. Still picture MADs are something different from any AMVs I've seen though. I wish I could find more of those (in high quality i.e. not YouTube). Beats watching clips of Naruto set to some Linkin Park with lip syncing and lens flares apparently being the most amazing editing out there.