Here’s a tutorial on making a graveyard for 15mm scale figures. It could easily be scaled up, though.
The Miniature Wargaming Editor
Working With Tree Armatures
Here’s a good tutorial on working with tree armatures.
Aquanautica Imperialis Submarine Rules
Aquanautica Imperialis is a set of free wargames rules for naval battles in the Warhammer 40K universe. The underwater rules are found here.
Making 15mm Hedges
Here’s a tutorial on making a 15mm hedges.
Cutting Form Hills Tutorial
Here’s a useful tutorial on cutting foam hills.