It's beginning to look a lot like Christmas ...

... which means cheap sources for terrain are available at your local dollar stores and craft shops.  I picked up a few miniature trees the other day, which normal people apparently use for purposes other than wargaming:

Note that in addition to the ubiquitous evergreens, I managed to snag a couple of deciduous trees for the gaming table, as you can see in the top row of the topmost photo.  I just need to go over all these with some green spraypaint and get them onto bases, and presto: new forest ambiance for Hordes of the Things or Song of Blades and Heroes.