Mitch’s Wargaming blog has a tutorial on making cheap trees for your wargaming table. It looks like a lot of work, but if you have more time than money …
Modeling
Modeling A British Colonial Blockhouse Fort
Here’s a tutorial for modeling a wooden blockhouse / fort.
Modeling Wooden Pallets
Wargame News and Terrain has a tutorial on modeling wooden pallets
Basing Figures On Washers
Here are some great ideas for basing figures on washers. This is exactly the technique (and the same fender washers) that I use.
Making Rocky Terrain From Wood Chips
Here’s a nice tutorial on making rocky terrain from tree bark chips.