"TheOne" posted a while back a post about
"get a sine wave from a 555timer"
The output of a 555 is a squarewave. Bascially (via fourier) all waveforms can be made up of sinewaves of different freq,ampl,shift.
The fundemental of a sqarewave is a sinewave - filter out all harmonics above the fundemental
As to a sqarewave voltage to an inductive load. There si no problem, this is hopw PWM controller work to control the voltage to a load (since the average level will be reduced by the duty). Only thing to watch out for is to ensure the current through the inductive load has a path to take when the voltage is OFF (ie via a free-wheel diode)