Now this list of HD channels may be incomplete or inaccurate, but this is what I have found so far. Some of these channels are speculative, but most do plan to do HD at at some point, and if not a channel of their own, then on another channel like inHD. Here's the list:
NFL Network
USA Network
E!
Wealth TV
Turner South
National Geographic HD
ESPN2 HD
HDNet Sports
HDNet Entertainment
Hallmark HD
A&E
The Tennis Channel
29HDNetwork
The Outdoor Channel
Turner HD
Gol TV
CNN-HD
Turner Classic Movies HD
THE Weather Channel HD
Lifestyle HD Channel (HGTV, Fine Living, DIY, Food Network, Network Channels )
These are all I have come across so far, but please remember some of these channels may never go HD, and some of them may comtinue to simulcast special programming on channels like inHD. Hope it helps