TerraGenesis has an article on making palm trees from toothpicks and scouring pads. They look pretty good, and would be just the thing for those Flames of War desert and pacific scenarios.
Modeling
Building Afghan Compounds
Matakishi’s Tea House offers a set of instructions for building Afghan compounds on a pay-what-you-want basis.
Weathering With Foam
Dark Future gaming has a post on using bits of foam to weather a 40K vehicle. The technique could be applied to almost anything, though.
Making Heavy Foliage Scenery
The Corbania Prime Blog has a nice illustrated tutorial on making heavy — jungle — foliage terrain pieces.
Tray Fillers
The Wargames Table blog has a good idea for filling in the blank spots on a movement tray.