Okay, for those of you with too much spare time, and $20-30 dollars to spare here's a pretty cheap way to make a very nice OGRE board. Keep in mind I haven't even attempted to try and make a "GEV" board yet, but I'll let you know when I do. I'm currently finishing a 40" x 40" board, but my first was a 24" by 44" miniatures scale version of the original, well loved barren wasteland from OGRE.
Step one, supplies:
*The cheapest plywood you can get ahold of, 1/4" thick is good, cut to size (I prefer 1" extra in both directions so I don't have to worry about getting everything right up to the edge).
*Big Bag o' Sawdust. They'll be happy to give you more then you need at your local hardware shop/lumberyard.
*Bottle of woodglue. I don't remember the exact size I used on the small board, but it wasn't enough, on the 3.5' square one I used the largest elmer size that doesn't have a handle.
*cheap paintbrush 1-2" wide.
*piece of scrap lumber 2"x4"x12" works well
*old bowl to mix in.
Step two, making a mess:
If you are finicky, or want really smooth terrain, sift your sawdust first to get the chunks out. I didn't bother.
In the bowl mix 3 parts glue, 3 parts sawdust, 1 part water. aproximatly. mix and add more of whatever you think approriate until you get a nice oatmeal consistancy... it'll probably actually look like oatmeal. Great!
Spread this gunk all over the board (I did mention do this outside or on newspapers right?) Try to get an even coverage. You may notice it's not sticking (needs more glue and sawdust) or it's clumping (needs more water and glue). Fiddle with the mix till you can get a nice even spread over the board. You don't want it thick, in fact you want about 40-60% coverage.
When you are satisfied put in a well ventilated area and let dry. This will take a while... like a day or two if it's humid.
Step three, breaking your fingernails:
Okay this is the most dangerous step of whole process. Remember that scrap 2x4 I mentioned? Take that and scrape your newely dried board. Hard, don't worry the woodglue has bonded on there pretty strong, all you're going to do is basically sand it. So you don't scrape your self while playing.
Step four, more oatmeal:
Okay, make some more sawdust, glue 'n water mix, this time with less or no water. Get yourself a cup of water you don't plan on drinking from, and a spoon. The spoon is for getting globs of goop outta the bowl. Dip your fingers in the water regularly so that the goop doesn't stick to your fingers while you're molding it.
Get a large spoonful and drop it where you want your crater. Flatten it, then push out from the center and in from the edges to make a crater. A little extra water on your fingers can make the outter edges meld with the terrain nearly seamlessly.
Get a smaller spoonful and drop in the middle of where you want your ridge, knead it out to form a ridge. When making a long ridge do a section at a time. You probably want to keep ridges/craters no more then 1/4"-3/8" high.