There are some interesting maps with impassable borders... Check the Maps subforum for "Siltrock" for a small one, and the Illwinter site (
www.illwinter.com) for the Middle Earth, which I think is pretty fun for a big map. It doesn't help SP that there is no diplomacy. Most of the players around here seem to be pretty good diplomats, though
I'm starting to think SP is good for just messing around, or trying expansion strategies... and that's about it.