A great looking set of 1x1foot tiles from Secret Weapon Miniatures (they also make top notch resin bases and pigments).
A little pricey for my needs, but already over $80,000 funded in 2 days!
[url]http://www.kickstarter.com/projects/1084069684/tablescapes-by-secret-weapon-miniatures[/url]
I know of several gaming groups that all pitched in to buy a set with the walls and other terrain bonuses.