How's this for a great idea...
http://www.ultrasonic-antifouling.com/index.html. Instead of using gallons of poison on the hull, you just epoxy on a little ultrasonic transmitter to keep the nasties off the hull.
According to http://boatbits.blogspot.com, an earlier version worked quite well. A little expensive, maybe, but given the cost of antifoul, it might only take a couple of years to pay off. Especially if you live in a climate where you could otherwise leave the boat in the water instead of hauling once a year.
Here's the specific post:
http://boatbits.blogspot.com/2009/11/electronic-utrasonic-antifouling.html
Interesting! While I don't have $1K (approx) to throw at it right now, it is definitely something to think about for the future...
I'm in the same boat as CapnK on this, although my boat is ferrocement. I inquired about the suitability of this for my boat, and the reply was encouraging, as the effectiveness depends on a rigid hull material to transmit the ultrasonic vibes. I've got that.
Steve