There are a lot of good sources for high res clips out there. I've bookmarked three good ones in my del.icio.us:
http://del.icio.us/plasticpool/sourcemedia
I don't know about where to get loops -- seamless, pre-looped loops, that is. There's a nice howto in the M8 manual for editing them, however. If you really want pre-edited loops, I'd ask on VJ Central (in my delicious, too).