Actually, the only thing I've managed to post to my little Web site deals exactly with this subject. Check it out:
Cheap Gaming Setup 101
As others have mentioned, unless you're really into building stuff, you're better off getting a few folding tables from Sam's Club. If you are really cheap like me, check Craig's List.
As for gaming surfaces, I haven't gotten around to writing that article yet.
However, check out the Flickr link in my signature and you'll see what a cheap piece of shower board
from Home Depot will get you. You can get a 4 ft. x 8 ft. dry erase surface for about $11.00. If you want a permanent grid, buy a drywall t-square
and an exact-o knife. The drywall t-square is a jumbo t-square and the long leg of it is a ruler. Then use it and the exact-o knife to etch out the grid. It took me about an hour to do. I don't think there is another way to put a permanent grid on it. I tried using an industrial strength Sharpie, but no luck. I have heard that eventually the shower board will stain. However, given that it is only $11.00, it's fairly cheap to replace. Personally, I have doubts that mine will ever be so bad that I will need to replace it. Also, I have found that, surprise, shower cleaner removes stains nicely.
p.s. Photos of my table are also posted to the Gaming Spaces Flickr group.