The Mini Stories blog has a nice photo tutorial on making snow bases.
Modeling
Scratch Built Machine Gun Nest
Here’s a photo essay on building a 15mm machine gun nest.
Making 15mm Vegetable Crop Fields
Big Lee’s Miniature Adventures has an illustrated tutorial on making model 15mm vegetable fields from corded dormats.
Making A Command and Colors Terrain Table
Small World Productions has a tutorial on making a “hex” based terrain table for Command and Colors.
Cheap 28mm Paved Roads
The Frozen Gamer has an article on making asphalt roads from vinyl strips.