In an e-mail to users, The DoubleClick Ad Planner team introduced new features including the 'Ad Planner 1000 list', Exporting Google Content Network Placements to Adwords and a feature actually rolled out in April, Ad Planner 'Lists'.
You can sign up for an Ad Planner account or check out the FAQs here or visit the help forum here.
It's a must view for media buyers (large and small) that haven't used the product before.
Curious what the 1000 top sites are? A static page is here.
Update May 27 7:20 PM ET : Barry Schwartz has an excellent piece at Search Engine Land referencing the just released AdWords blog announcement and more.