I'm with Eden - although the winter shoes sounded/looked tempting, I can't really afford yet another pair of bike shoes so:

I wear my mountain bike shoes which are a tad bigger with SmartWool socks...as the temps drop I add toe shoe covers and eventually full shoe covers and SealSkinz socks and my feet stay quite toasty warm! now......if I could just figure out how to keep my butt warm it'd be perfect!