I've never had a campaign run so good as the one I'm currently running, which is:
Lost City of Barakus (Necromancer Games, city & surrounding wilderness, levels 1-5; I've run it levels 2-6)
Red Hand of Doom
LCoB was a great city setting with a similar "frontier" theme as the rest of the Vale in RHoD. I just renamed it Dennovar (the most Easterly of Elsir Vale's cities) and kept the bureaucracy as written in LCoB. They don't flesh out Dennovar in Red Hand anyway, so it was easy.
A couple random side-treks lead the PCs to go to Brindol (they were originally from there, so they already had some info on it) and a couple of the little towns nearby, all to get a sense of the Vale, and then back to Dennovar and finish up the dungeons of Barakus, and fighting the Lich therein.
This was nice because I also tied the Lich in Barakus to the Lich in Red Hand (The Ghostlord, I believe he's called), giving the PCs some extra foreshadowing. Furthermore, I tied some of the dragons from Red Hand with the dragons in LCoB, for added foreshadowing.
All-in-all, it was like the two modules were meant for each other!