http://www.avsforum.com/avs-vb/showt...2&page=1&pp=30
I plan on adding HD to my DirecTV package as soon as we finish building the home theater (of course, we have to
start building it first). The link above is very incomplete, at least for DirecTV. It doesn't look like it's been updated in a while, because I know NGC is available in high-def over DirecTV. It seems like they tell you during every single commercial break.