A source for listings for the new HD channels I've found appears to be uk-tv-guide.com, but you have to click on the programmes to confirm if they're actually in HD or not and it does show some programmes as being in HD when they're not (eg The Wire on FX HD) so I'm not hugely impressed. Here are the pages for today:
Channel 4 HD
National Georgraphic HD
No ESPN HD yet but that's not broadcasting until 8pm tonight.
Does anyone know of a more accurate set of listings?