Major Thomas Foolery has a photo tutorial on making WWI era German East Africa administrative buildings.
The finished product is quite impressive.
Modeling
Modeling Tall Grasses
Here’s a photo tutorial on modeling tall grasses, using old brushes.
It looks like you’d be able to get quite a bit of material out of one of those cheap house painting brushes.
Modeling Troy For Skirmish Gaming
While not quite a tutorial, 15mm Wargaming for Fun and Sanity has a great article on modeling a mud brick / adobe town. The build was designed for ancient Troy, but as the author notes, such buildings are extremely versatile, applicable to more periods than you can count — even science fiction.
I’m inspired.
Making A Pill Box
Wargaming Miscellany has a photo tutorial on making a bunker out of a hexagonal craft store box.
It is amazing what you can do with just a little imagination and things not intended for the task.
Making A Raft
Wee Blokes has some instructions on making a raft for your miniature wargames.
The core materials are sticks picked up on a walk in the woods.