Lords of Madness (aberrations done right; I don't think we'll see their like again in 4th edition with the changes to monster types)
City of Brass (awesome setting, who knows if it will fit into 4th edition's cosmology)
Shackled City Adventure Path (love it or not, its the adventure which epitimises the heart of 3rd edition, rules bloat and all)
I'd be tempted to put in an honourable mention for War of the Burning Sky, but there's a fair chance it will be getting an update to 4th edition anyway.
City of Brass (awesome setting, who knows if it will fit into 4th edition's cosmology)
Shackled City Adventure Path (love it or not, its the adventure which epitimises the heart of 3rd edition, rules bloat and all)
I'd be tempted to put in an honourable mention for War of the Burning Sky, but there's a fair chance it will be getting an update to 4th edition anyway.