I locked my bike outside, in the elements, for an entire Seattle winter last year. It is a Giant OCR1, which has an aluminum frame and carbon fork. The bike was fine, I had zero issues with the bike itself from all that exposure to the wet and wind.

However, that is probably what did in my Cateye Strada Wireless computer; the display stopped working towards the end of winter. The CygoLite Dualcross I used most of last winter made it through all that fine though (dumb, I know, to leave a $150 light on a bicycle, but actually my blinkie is the light that got stolen one day).

Lubricate your chain regularly, give your bike a good cleaning now and then, and you'll be fine.