I went to a vocal strengthening expert once, and this was one of the excercises she had me do...
start at an F above middle C, and very softly sing the syllable, "Hee." sustain it for as long as you can (do not exceed 60 seconds) with absolutely no vibrato. it will start to sound really weird...a sort of ringing in your ears. go up to F#, then G, then G# then A. stop at A. go back down again.
the longer you can sustain the notes, the stronger your voice (both singing and speaking) will be.
and NEVER speak in the gravely voice we all have in the morning. warm up every morning with those things so that you don't damage your voice at all (I, myself, am anal rentitive about those things).
hope this helps!
"you can take the girl out of Hicksville, but you can't take the Hicksville out of the girl." ~Rent