sir_ollibolli said:
Kalamar, Midnight, Dawnforge, Demon Wars, Karathis, Skull & Bones, Morningstar are too similar to make planar hopping.
Well, I have to disagree with the Kalamar part of that argument at least...
It depends where the gate is, as to how similar it is to another setting. For example, Kalamar's Svimohzish Isle would be similar to Nyambe, which you do recommend. There are also dark evil theocracies, slaver nations, and hobgoblin nations, any of which could be used as a major departure from the norm. The tendency toward racial tensions and suspiciousness of strangers might cause problems, depending on the PCs' appearances. Also, the language challenge would be the real problem for visitors, since the KoK setting doesn't expect that everyone knows a "Common" language.
Anyway, some planar travel ideas for the Kingdoms of Kalamar, should it be used. These come from the core campaign setting book:
City of Ardarr-Norr: Having been to the astral plane once, the wizard Nabaddan is eager to return there. A close call with a hunting party of githyanki left him flush with excitement. Nabaddan does not sell items or services, but he will purchase magical items that allow extraplanar communication or travel.
The Riftmaster: This collection of stars forms a key. It is visible during the winter for two months. The Riftmaster illuminates the sky one minute before midnight on New Year’s Eve. It is believed to open extra-planar gates worldwide for one minute, allowing any creature to pass.
Village of Trarr: Sages insist that homely Trarr stands at a delicate juncture between the planes. While the juncture is not a dramatic threat to the world, it does mean that certain outsiders pop in and out around the city more often that the locals would like. Celestial and fiendish creatures appear among the local wildlife from time to time, as well as mind flayers, abishai, and ethereal filchers.