The Wargames Table has a very useful article on making magnetic basing. Using a magnetic system can be useful both for movement trays and for transport.
For my part, I base all of my 28mm figures on one inch washers. Then, I line both movement trays and transport boxes with magnetic vinyl, of the sort used for signs for the sides of cars.
I’ve also found that I can paint the magnetic vinyl with no loss of magnetism. So, my movement trays have a green surface onto which the figure bases stick.
Here is a photo tutorial on making wargames buildings from foam blocks and balsa wood.
Lair of the Uber Geek has an article on modeling mud. The key ingredient is liquitex modeling pasted. I have used this myself to great effect.
This is a bit esoteric, but the Massive Voodoo has an interesting article on seeking out roots to use as bases for display miniatures. They’d also make some really cool and alien looking tabletop scenery.
I’m reminded of something that John Hill, creator of Johnny Reb, said to me years ago: Nature recreates itself in miniature. Thus, chunks of bark look like rock formations, tree branches retrain the structure of trees, etc.
Wargaming Hall of Famer John Hill (Squad Leader, Johnny Reb, et. al.) once said to me: “Nature reproduces itself in miniature” when I asked about some of the beautiful home made terrain on his tabletop. That’s certainly true about this technique for turning leftover pumpkin stems into tree stumps.