There are two solutions I'd suggest. The first is to string an Ethernet cable, with a repeater. The Ethernet specification says that cable runs without repeaters have to work at a range of 100 meters. There's nothing stopping you trying to work with 200 meters, though it will get flakier with added distance.
Alternately, you can buy a Ubiquiti Nanostation (A Seattle retailer sells them: http://metrix.net/ubiquiti-nanostation-2-ns2-p-110.html -- disclaimer: friend of mine). You may wind up having to mount it on a pole, as trees and terrain are horrible for wifi signals. You'll pretty much need line-of-sight.
I've worked with Nanostations before, and I highly recommend them. They're really nice: they come with a pole mounting, are pretty much weatherproof, only require a single cable (the network and power are run in the same cable) and have really handy signal-strength lights directly on the unit.