Casejunkiez.com have posted up a review on the new Enermax Speed-Dial 80mm fans. Heres a snip:
Another means of keeping the noise levels down inside a PC is to be able to control the speed at which these system fans spin. The Fan Bus has been a very popular add-on to PC cases, initially allowing fans to be switched on, off and even run at half speed. Then came the Rheobus that allowed a user to completely vary the speed of their fans manually with the turn of a dial.