Here’s a useful tutorial on cutting foam hills.
Here’s a brief article on making some small cork tile hills. I like the effect.
Here’s a post on making small hills from corkboard. What I want to do is to make a series of terrain tiles from cork. I just need to find a relatively cheap supply of 1 foot square cork tiles.
The Legends and Legions blog has a set of instructions for making a nice set of stepped hills for a Judean campaign. I’m interested in this because I have Judean, Assyrian and Philistine armies in 28mm.
Kevin’s Miniatures and Hobby Table Blog has a photo tutorial on making small hills out of cork.