I am in the process of making my own. Here is a good guide on how to start:
http://www.miniwargaming.com/forum/viewtopic.php?f=7&t=43449&st=0&sk=t&sd=a, you can get an 8 foot by 4 foot piece of that pink foam from about $15-$25 depending on thickness from Home Depot. I also grabbed a large piece I believe 4'x8' of
mdf/particle board to put my terrain on, I heard this helps durability and weight it down a bit do it does not move easily if bumped. I was able to use a dremel and I cut out various shapes out of the board, including a river in different sections and bends, some 1inch wide pieces too add that lightweight wood you can get from Michaels or even popsicle sticks would work for fencing. I then sanded down the edges. For forest I bought some of these trees here:
http://www.sweetwaterscenery.com/page6.php?category=4&view=productListPage a pack of 5 was roughly $20, expensive yes, but they look good. I attached a rare earth magnet to the bottom of them with some green stuff and glue and then another magnet to the base of a forest so the trees are removable. For the river which I am still planning on building, I will sand down the middle where the water will flow, then add a glossy blue plaint then cover with woodland scenics realistic water with sand and grass on the banks. It will have spent about $75 after paint, sand and glue as well as the previous things mentioned but I can cover easily 4 tables worth, if you have some friends with their own tables split it with them. Also don't forget lakes and marshes and swamps which can be made. The only thing I am lacking is buildings, I do plan on buying the
GW fortified manor for the value it has fences and walls, a tower and a small building. Also check your pet stores, aquarium scenery would work great too.
