Buttercup
Princess of Florin
Well, my collection ony includes 3e stuff, but of that, I'd say Bluffside is the best for sheer imaginative beauty. Geanavue has higher production values, but would be a bit of work to remove from Kalamar. Freeport is also a physically gorgeous book, and the city is way cool. I like Splintered Peace as well, though the details involve mature themes so it might not be for everyone (by mature, I don't mean Junior High tittilation, but themes that I wouldn't be willing to DM with any players other than serious adults, eg. racism).