A good news today, WB has given us a new info on HBP trailer- The worldwide 'proper' teaser trailer (generally a teaser trailer is less than a minute), will be released via satellite on 29th July, 2008 (Tuesday).
Hopefully it will be online soon after it will be released on satellite. And it will be probably also shown with 'The Mummy', which will be relased on 1st August (in US).
A big, 2 min+ trailer will debut sometime in August-September, most likely with 'Star Wars: The Clone Wars' which is going to be released on 15th August.
Keep checking for new news!