Now that we have a new judo yellow belt, we are about to get into (among other things) hadaka jime - the rear naked choke. Here's some good video to study up on between classes. First, a general demonstration of a handful of variations...
And now, Kashiwazaki demonstrating one of the coolest, smoothest entries I've seen. It starts out looking pretty mundane - even to the point of tori seeming dull and inexperienced, but it's a trick, and even seeing it the second time I thought it was really fine!
And here is a link to the best RNC tutorial I've seen anywhere on the net. This is Stephan Kesting demonstrating Rear Naked Choke finishing for Aesopian's BJJ blog. Enjoy.