Most of the three speed hubs we do are the venerable and excellent Sturmey Archer AW. This is a great old bit of kit. It's really easy to explain; slow medium fast.
The old ones have a somewhat annoying "no drive" position between second and third, so if the cable is not adjusted correctly this can happen. The new production use a ball locking internal which eliminates this.
To adjust a three speed, click here.
Sturmey Archer's 3 speed fixed gear hub is being re-introduced. Details can be found here.
More will appear here soon.