I just saw that Korber has released their HO modular building system. Looks like you can do a lot with it.
Yeah, this looks like an infomercial to me, too. On the other hand, there are some interesting items here. The modular walls are very inexpensive, like 69 cents a piece, and the support stuff and roof pieces are in the same range. I did a quick non-order to find out shipping, and it came out $4.50 for either 1 or 10 of those 69-cent pieces.
Has anyone seen the product in the flesh?