I will be building a windturbine I need your help!

[derricka]

Michelinho's idea is a good one. While a chain and sprocket is a little mechanically less efficient then direct gearing, it should allow you to determine the best gear ratio at low cost. Once you know the ratio, you can switch to direct gears. Also remember, the torque required by the generator or alternator varies in proportion to the electrical load connected to it,  So if I was designing a wind system, I would start with the electrical requirements, and work my way back toward the alternator, and finally the blades.

[Mark69]

If you can find a used drill press w/i your budget, maybe a bad motor or something old, they have many different pulley sizes in the top for different gearing to control the speed of the bit.  They use belts as well so it would take less draw to spin them.  Or you can use the design style of a snowmobile, uses belts and cones, like a constant speed transmission.  This would be more expensive but is the ultimate in gearing.
Mark

[Blacksmith]

Infringer
   I have been around a lot of windmills and wind generators and have worked on a few with my dad when I was growing up.
Some rules of thumb: 1. Any more than three blades and they start running into old air.
                                2. Dont use blades any heavier than is structuraly necessary.
     
There are others but those two should be seriously pondered over.

Blacksmith

[derricka]

Infringer,

I noticed that your shopping list didn't include a rectifier, voltage regulator or batteries. In addition, if you want to convert the battery power to standard AC, you will also need an inverter.
While you may already have these items, I just wanted to make sure you didn't overlook them.

[Paul-R]

I wonder how an anemometer type windmill would work - i.e. with huge cups.
http://www.sciencescope.co.uk/images/anemometer.jpg