I've taken a stab at making an interactive kite size / body weight / wind speed / board size calculator. Check it out and let me know what you think. http://jimbodouglass.blogspot.com/2011/ ... lator.html
Basically, you just put in your body weight and it recommends the ideal kite sizes for various windspeeds. For the boards you put in your body weight and it recommends the sizes for beginner, light wind, medium wind, and high wind twintips. I haven't put surfboards, skimboards, or raceboards into it.
It probably won't be very useful for good kiters who already know what stuff they need for what conditions, but I think it might be helpful for folks who are just starting out, especially if they are lighter or heavier than usual and need to make sure they get stuff that is proportional to themselves.