Was doing a bit of research on wind turbine components.
My interest was in both the main components and the sub-components. The primary components of a wind turbine (and the associated wind power plant) are as follows:
Primary Wind Turbine Components
- Blade
- Shaft
- Gearbox
- Generator
- Nacelle
- Tower
Other Wind Turbine Components of Importance
- Rotor
- Yaw mechanism
- Anemometer
- Brakes
The rest of the components that complete the wind power plant include
Our specialty focus areas include 
- Power converter
- Transformer
While reading up on the above, some of the web resources I came across were quite good; thought it could be useful to many other who could be interested in this topic as well
Parts of a Wind Turbine Explained – Source: NREL
Capital Cost Breakup for Wind Turbine Components – Source: Industry Canada
The two pictures above say it all; both in terms of the key components, and which are the most costly components.
For those of you who would like to see a gearbox at close quarters:
Wind Turbine Gearbox – A Close Look
And another picture that illustrates the various parts of a wind turbine gearbox
Inside a Wind Turbine Gearbox (courtesy: EE&T)
Some other links that could be of use:
Anatomy of a Wind Turbine – from AWEA
Breaking down the cost of wind turbine components
Structure of a Modern Wind Turbine
