find an old steel frame with horizontal dropouts and go to sheldon brown's site.
pawn shops, craiglist or garage sales are great if you are of average height.
did I say steel? yes, get steel. aluminum is harsh and has a short life-span if ridden hard.
when you find a frame, post it up.
I commute on an early 80's motobecane mirage geared at 52-18.