Sarissa precision had their range of laser cut MDF and greyboard buildings. I did not quite run amok (I had to trim my list a bit), but I did buy a number of buildings for a range of periods.
As I mentioned earlier, I bought the WWX starter set last year.
The figures are taller than normal "28mm" so when Sarissa announced they had a new 40mm Wild West range, I thought that was a sign.
I bought the Adobe Jail and one of the small shops as a start.
I bought the Survivor Shack at SELWG, and thought the "Ghost town" barn and the picket fence would be good additions.
The burned out cabin I thought would make an additional feature for post-apocalyptic games.
Empress and Gringo's 40 are starting ranges of 28mm Vietnam figures, and I thought that some of the Colonial/North Africa ranges might work until there is a specific Vietnam buildings range.
There were also two buildings for World War 2 that interested me.