I promised a while back to talk a little bit about some downloadable paper terrain kits produced by Dave Graffam Models. I really like these kits a lot. They are very reasonably priced (about $2 each on average), offer tons of detail, and many have multiple layers allowing you to customize to your preference. The only downside that I have found is the time it takes to build. I'm guessing on average you will spend a few hours on a kit sized like the stone church you'll see below (I use these for 25/28mm, so less time would be required for smaller scales).
The method that has suited me is to print on 8.5 x 11 copy paper and use as skins I glue to black foam core (I use 3M spray adhesive but I imagine a thin film of white glue would do just fine). I then cut my pieces and use super glue and butt joints to assemble.
These kits can be found on Wargame Vault (www.wargamevault.com) and there are freebies every now and then.